#56 Implement multiple 'action' items for different mouse clicks

[Sy Ali]

Implement Action2, Action3, etc.. for mouse2, mouse3 and any other mouse button.

Implement a generic "scroll up" and "scroll down"

This would also resolve [ 1701230 ] scroll over 'show desktop' plugin to change desktop
http://sourceforge.net/tracker/index.php?func=detail&aid=1701230&group_id=66031&atid=513128