Plugin API features

[MarcLandis]

Lets discuss what functions the plugin API needs to have.

My first thoughts:

- find/load plugins from a sub folder
- unload plugins
- each plugin needs to create a tab page in the settings if needed
- saving settings can be in the main settings file or per plugin
- probably a lot more...

[eitanpo]

- Settings for plugin can be a simple checkbox or collection of name-values, and values can be from different simple types or structures of simple types, and added dynamically to the form.
- Plugin might add items to the context menu
- Plugin might control some parts of the program
- Plugin will receive different events from the program. This requires another interface IApplication

We can start by converting simple features to Plugins, like send info to Messenger and Xfire.
Last.fm plugin probably will be the most complicated one.