Hendrik Leppkes:
	- Add a fallback for GetNumDungeonMapLevels, which can return nil on the Legion Alpha.
	Minor intentionally not bumped since this change is only needed on the alpha,
	but would need a full data update to take effect, which would only add overhead on live.
	
	Reported by Gethe and MysticalOS on IRC, fix tested by MysticalOS.
	- Add the confirmed Draenor zone finale scenarios to the instance overrides
	- Add the proper Garrison Level 2 instance IDs
	Fixes ticket 5.
