Taking a first stab at the plugin system

Jose and I taking a first stab at a plugin system for opencafe.
* Making more changes
* Adding simple docstring
* Cleaning up a plugin install a tiny bit
* Adding license to __init__.py files
* Adding Plugin List
* Adding note to the end of setup

Change-Id: Id0a61549f37ada7f9a254f8cc944957c4d2c4694
Moving skip on issue into a plugin

Change-Id: Iae4e4b78832f54e2483ef41214690a513677ca34