Added RT, LT and Guide (and btn-dull)

There wasn't a grey button, so I added one (btn-dull)
Added Buttons for:
- Right Trigger (rtrigger button ID)
- Left Trigger (ltrigger button ID)
- Guide/Overlay (guide button ID)
Added hover/active/focus for btn-dull
Merge pull request #1 from BenWoodford/master

Added RT, LT and Guide (and btn-dull)