Implemented plugins for reports.

Generously copied from: http://martyalchin.com/2008/jan/10/simple-plugin-framework/
Change ReportProvider to PluginProvider.

This makes the plugin provider a generic plugin. The plugin will define what methods it has available to it, such as report.

The documentation on the PluginProvider class will define how to build a plugin.
Moved Trello oauth token gathering to init.

Also removed some commented code.
Moved Trello class to plugins dir.
Merge pull request #5 from matthew-parlette/pluginmount

Pluginmount