WowAce

Hendrik Leppkes:
    - Small fixes.
    - Implemented a macro button (very basic functionality, only shows icon and macro text)
    - Implemented a item button.
    - Implemented insecure drag handlers (In Pre/PostClick) to allow clicking on buttons to drop of the action (out of combat only)
    - Refactored OnDragStart/OnDragReceive secure methods to allow callign them from insecure code.
    - Converted states to string instead of numbers ("vehicle" can be a state, instead of some opaque number)
    - Added lookup table for SpellBook Slot -> SpellId
    - Disabled pet type for now (non functional)
    - Added comment about library upgrading.
    - 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.