Add get_selections() and set_selections() for dpkg.

This module will enable to freeze a package at a certain version, with the "hold" state.
Add TODO, amend later... FIXME.
Merge my dpkg-selections branch with develop.

Resolved conflicts in modules/apt.py.
Fix merge mistake.

urllib2 and json is part of standard Python.
Use yaml.safe_load()
Add another TODO
Use code-block

As per @terminalmage suggestion.
Changed name spaced event tag separator from "." to "/' dot to slash to enable
minion ids that are domain names inside tags.
Updated constant delimiter value
Also fixed fileserver tags that were not being created with tagify so that in the future
any changes are automatic.

In general users should use the tagify function to create tags to ensure
correct separators etc.
SuSE based distributions get the `gid` from `users` not the `gid` from it's name. Fixes #7003.

Full explanation about why is this can be seen here:

  https://github.com/saltstack/salt/issues/7003#issuecomment-23813071
Use the `requires_system_grains` decorator from salt-testing
Use raw strings in regular expressions. Double to single quotes.
return after exception is caught.

Otherwise, it is overwritten after 'returner' is evaluated and set result to True ... which is inaccurate.
Merge pull request #7048 from s0undt3ch/issues/7003

SuSE based distributions get the `gid` from `users` not the `gid` from it's name
Merge pull request #7049 from s0undt3ch/hotfix/jenkins

Use raw strings in regular expressions. Double to single quotes.
Merge pull request #6882 from holmboe/dpkg-selections

dpkg selections
Added sls and pillar as params

This change is backward compatible...but untested.
Merge pull request #7038 from SmithSamuelM/develop

Changed name spaced event tag separator from "." to "/' dot to slash
Merge pull request #7050 from VertigoRay/patch-1

return after exception is caught.
Merge pull request #7051 from whiteinge/jenkins-sls-param

Added sls and pillar as params
Add salt-thin version file