Improved supervisord management is critical for maintenance of instances
between tests.

/reviewed-on !504

In preparation for moving this to a better place, use the same code in
all the places where this code was duplicated.

Reconcile all implementations, document a little bit more the methods
and the future plans.

When slapos.libnetworkcache is not installed, then shacache is not
enabled, so SR will no longer build when there's a dead link.

/reviewed on !379

Filename is split as an URL path, and joined in OS-dependent manner.
Remove corresponding comment in all buildout.hash.cfg files.

an utility method to control and query supervisor instance used by
slapos using http://supervisord.org/api.html

Some files and sockets where created in their default location, which
was in the software.
As a result, this software was working only on webrunner or testnodes,
which uses same unix user for software and instance.

fix all getInstanceParameterDict typos

supervisord creates a socket with pid in the name, so we have to account
for the space of pid.

Because it's not so easy to know the max size of pids, we just assume 7
places.

otherwise we leak zombie slapproxy processes

fix getInstanceParameterDict typo

To run tests locally by `python setup.py test`

This is a new kind of test suite that compile software, request instance
with specific parameters and check that the instance works as expected.