Improve comments.
Better error message and remove unnecessary file.
Fix a bug in creation of EnumerateListBlock.

Case: FOR A in B
ended up with inVar and outVar being the same.
Change a getBlock call and improve exception message.
Improve an exception message.
Try to fix bugs in EnumerateListBlock.
EnumerateListBlock: forward documentCollection in DOCVEC case.
Add facility to AqlItemBlock to save some copying.
Implement steal for AqlItemBlocks and use it for FilterBlock.
Merge branch 'aql2' of ssh://github.com/triAGENS/ArangoDB into aql2

Conflicts:
	arangod/Aql/ExecutionBlock.h
	arangod/Aql/Types.h
Merge changes for steal in.