This supports the case where some paths used for shared parts are
symlinks

Empty paths confuse the ldd check, because empty prefix always look
valid, so executables using system libraries will be considered as
valid.

This should prevent such confusing tracebacks when building software fail:

    INFO Finished software releases.
    ERROR:slapos.testing.testcase:Error during request destruction
    Traceback (most recent call last):
      File "parts/slapos.core-repository/slapos/testing/testcase.py", line 615, in _cleanup
	cls.requestDefaultInstance(state='destroyed')
      File "parts/slapos.core-repository/slapos/testing/testcase.py", line 680, in requestDefaultInstance
	cls._instance_parameter_dict)
    AttributeError: type object 'SlapOSInstanceTestCase for ...' has no attribute '_instance_parameter_dict'

This reverts commit 49ec3ece.

That commit revealed that all the rpath check was not effective and that
we have in fact lots of components which use system libraries.

We'll fix rpath on slapos profiles and only then we'll fix this check,
to prevent test failures (even if the test failures show a real problem)

This changes a query like:

    SELECT date FROM user WHERE reported = 1 AND date != '2020-04-13' AND date != '2020-04-12'  AND date != '2020-04-11'  AND date != '2020-04-10'  AND date != '2020-04-09'  AND date != '2020-04-08'  AND date != '2020-04-07'  AND date != '2020-04-06'  AND date != '2020-04-05' AND date != '2020-04-04'  AND date != '2020-04-03'  AND date != '2020-04-02'  AND date != '2020-04-01'  AND date != '2020-03-31'  AND date != '2020-03-30'  LIMIT 1

    EXPLAIN QUERY PLAN ...
    0|0|0|SCAN TABLE user USING COVERING INDEX user_date_reported_index

which took ~3 seconds on a 1.5Go collector.db into:

    SELECT date FROM user WHERE reported = 1 AND (date < '2020-03-30'  OR  date > '2020-04-13')  LIMIT 1

    EXPLAIN QUERY PLAN ...
    0|0|0|SEARCH TABLE user USING COVERING INDEX user_date_reported_index (date<?)
    0|0|0|SEARCH TABLE user USING COVERING INDEX user_date_reported_index (date>?)

which is instant.

See merge request !201

This changes a query like:

    SELECT date FROM user WHERE reported = 1 AND date != '2020-04-13' AND date != '2020-04-12'  AND date != '2020-04-11'  AND date != '2020-04-10'  AND date != '2020-04-09'  AND date != '2020-04-08'  AND date != '2020-04-07'  AND date != '2020-04-06'  AND date != '2020-04-05' AND date != '2020-04-04'  AND date != '2020-04-03'  AND date != '2020-04-02'  AND date != '2020-04-01'  AND date != '2020-03-31'  AND date != '2020-03-30'  LIMIT 1

    EXPLAIN QUERY PLAN ...
    0|0|0|SCAN TABLE user USING COVERING INDEX user_date_reported_index

which took ~3 seconds on a 1.5Go collector.db into:

    SELECT date FROM user WHERE reported = 1 AND (date < '2020-03-30'  OR  date > '2020-04-13')  LIMIT 1

    EXPLAIN QUERY PLAN ...
    0|0|0|SEARCH TABLE user USING COVERING INDEX user_date_reported_index (date<?)
    0|0|0|SEARCH TABLE user USING COVERING INDEX user_date_reported_index (date>?)

which is instant.

This supports the case where some paths used for shared parts are
symlinks

for nexedi/slapos!725

```
RuntimeError: /srv/slapgrid/slappart9/srv/testnode/cxm/inst/test0-0/tmp/soft/503f3967022ee2febfbb1f4cb30c3a0f/parts/theia/node_modules/puppeteer/.local-chromium/linux-722234/chrome-linux/chrome has some not found libraries:
	libX11-xcb.so.1 => not found
	libXcomposite.so.1 => not found
	libXcursor.so.1 => not found
	libXdamage.so.1 => not found
	libXfixes.so.3 => not found
	libXi.so.6 => not found
	libXrender.so.1 => not found
	libXtst.so.6 => not found
	libnss3.so => not found
	libnssutil3.so => not found
	libsmime3.so => not found
	libnspr4.so => not found
	libcups.so.2 => not found
	libXss.so.1 => not found
	libXrandr.so.2 => not found
	libasound.so.2 => not found
	libatk-1.0.so.0 => not found
	libatk-bridge-2.0.so.0 => not found
	libpangocairo-1.0.so.0 => not found
	libpango-1.0.so.0 => not found
	libcairo.so.2 => not found
	libatspi.so.0 => not found
	libgtk-3.so.0 => not found
	libgdk-3.so.0 => not found
	libgdk_pixbuf-2.0.so.0 => not found
```


See merge request !200

See merge request !199

 * xml2dict and dict2xml support the JSON format of parameter dict
 * since xml2dict doesn't support unicode, we convert unicode to str in
getInformation

See merge request !198

 * xml2dict and dict2xml support the JSON format of parameter dict
 * since xml2dict doesn't support unicode, we convert unicode to str in
getInformation

The example from `software/slapos-sr-testing/README.md` in slapos repository uses a path with `~` for shared parts, but this was not supported.

Also, what was not supported is to use `setUpModule` more than once, but erp5 SR tests are starting to do this.

See merge request !196

In slapos:manager_list it is possible to enable list of managers, but as they
have to be configurable support sections for each manager by [manager:x]

So having configuration file like:

[slapos]
manager_list = mgr

[manager:mgr]
key = value

Will allow for the mgr manager to read values from manager:mgr

Slapos is started the first time the StandaloneSlapOS is instanciated,
then, in each class teardown we stop slapos, so the second time
setUpModule is executed, the slapos is not started yet.

Start it one more time in setUpModule to ensure it's started in this
scenario.

In cloudooo software release we are installing libreoffice and wkhtmltopdf as binary.
These parts contain executables that seem to have missing dependencies, but there are wrapper setting library path, so they can be ignored.

See merge request !195

python interpreter is sometimes referenced only in bin/buildout's
shebang, even if not used anymore in any software, if it was used to
initially created the buildout. In that case, the part should still be
considered as used and not pruned.

See merge request !194

Some information (like the actual buildout command used to invoke buildout ) is shown only when slapos node runs with `-v`

See merge request !190

python interpreter is sometimes referenced only in bin/buildout's
shebang, even if not used anymore in any software, if it was used to
initially created the buildout. In that case, the part should still be
considered as used and not pruned.

When running with shared parts from slaprunner, we'll have path with
double slashes like:

    /srv/slapgrid/slappart3/srv//runner//shared/libexpat/468993ea3777c1a342102bc1c4b43425/lib/libexpat.so.1

because slaprunner has some paths with double slash.

See merge request !191

In this way is possible to follow up deployments more closely.