Fixes PEP8 issues as reported by tox and unittests

 * Changes docstrings from single to double quotes.
 * Reformats multiline declarations with non-visual indentation.
 * Turns rsyslog resource into a plugin
 * Moves plugin-specific unittests into their respective plugins
 * Add tox support to plugins with tests

Change-Id: Ife172b165004c366ad64faa7c00afceb8e99c76d