working on comparison function for AqlValues.
Merge branch 'aql2' of ssh://github.com/triAGENS/ArangoDB into aql2
same as last.
Merge branch 'aql2' of ssh://github.com/triAGENS/ArangoDB into aql2

Conflicts:
	arangod/Aql/Types.h
added new global function triagens::aql::CompareAqlValues.

Also made associated changes in SortBlock.execute().
Merge branch 'aql2' of ssh://github.com/triAGENS/ArangoDB into aql2