If backend does not send Content-Type the frontend is responsible of adding
correct one.

Not use erp5-doc as a submodule anymore

/reviewed-on !613

Usually when we make change to SlapOS profiles, we only check the result of SR test and sometimes problems in the json schema are introduced and we only notice this when we check the result of `SLAPOS-EGG-TEST`.

This MR is about:
  - also running `slapos.cookbook` tests as part of `SLAPOS-SR-TEST`. This test in fact contain both "egg tests" for some recipes in nexedi/slapos repository and "lint test" for the formatting of json schemas for parameters (because this nexedi/slapos repository contain both some recipes and profiles).
  - fixing current problems with json schemas on master branch.

/reviewed-on !612

according to rfc4329, text/javascript is deprecated in favor of
application/javascript, so make sure we also compress the "official"
mime type for javascripts.

/reviewed-on !609

Now that we also run slapos.cookbook tests from SLAPOS-SR-TEST we cannot
simply examine buildout.cfg, because unlike SLAPOS-EGG-TEST this
repository is now checked out in parts of the software folder, not the
instance folder.
So that trick of looking up the egg directories in buildout does not
work, because this is a software buildout.cfg ... instead, we assume
that the standard eggs and develop-eggs directories are used.

Use the new URL that are worldwide accessible

Added part for logrotation into part_list, resulting with installing it.

/reviewed-on !606

Use the latest firefox and geckodriver to support file uploading tests.

This reverts commit 9b0f4f7d.

[firefox] Use firefox 60 by default to use DataTransfer approach for file uploading functional tests.

Commit ba6c3331 does not handle non-string
values properly. While fixing this bug, I also found that '-init' was bad:
sections were uninstalled on next runs, which is a problem with recipes
whose install() return paths.

This reverts commit 0931ebe9.

Commit ba6c3331 has a bug breaking
the ERP5 SR unless incremental catalog backups are disabled.

  Now the egg contains the missing dependency

0.4.59 has a missing dependency to 'six' and breaks too many things.

  Update the stack/slapos.cfg to use the newest version

  Remove duplicated version definition at software level to prevent excessive duplication
  of the value.