Plugins should be pulled in from a seperate repo

[seamustuohy]

Plugin's are currently kept in a sub-folder of the project. This makes the process of adding or removing plugins require forking the entire co-pilot project. If the plugin directory was cloned from a seperate repository and placed in a separate plugin directory it would solve this. The changes that I propose are as follows.

• Add a plugins_repo, plugin_branch, and plugins_directory environment variable in the install script
• Have plugin install scripts leverage plugin variables when installing.
• update the logic that currently imports plugins to import from the new plugin location.
• Have supervisor scripts leverage the plugin variable when defining where plugins are located.
• Issue If a.git directory exists in the plugin directory it will test every .git sub-directory as a possible plugin. #126

This will make plugin development far easier.

[seamustuohy]

The plugins variable in the main install script should be in a repo:tag format to allow for plugin releases to be specified through tags. This will make testing plugin development and plugin releases far easier.

[seamustuohy]

This needs to update the logic that currently imports plugins to import from the new plugin location. We should add the plugins directory to the PYTHONPATH and then import from plugins import <plugin>

[seamustuohy]

Supervisor scripts have been updated in the plugin repo in the issue 124 branch

[seamustuohy]

Fixed on branch 124 which was merged into master within #132