WowAce

Hendrik Leppkes:
    - Removed another debug line.
    - Added an option to disable Drag'n'Drop of the buttons (for non-action buttons)
    - Apparently PickupSpell works with spellids instead of spellbook slots now.
    - Simplify updating after drag'n'drop
    - Fix button updating after drag'n'drop.
    - Update the button once after creation, and some comment updates.
    - Add two new generic spell events to the handler and remove an unused inventory one.