finding index in CalculationNodeFinder.
fixed bugs in last.
added clone method for execution plan, removed debug prints.
more IndexRangeNode stuff
fixing replaceNode for ExecutionPlan.
Merge branch 'aql2' of ssh://github.com/triAGENS/ArangoDB into aql2

Conflicts:
	arangod/Aql/OptimizerRules.cpp
removing debug comments.
Merge branch 'aql2' of ssh://github.com/triAGENS/ArangoDB into aql2

Conflicts:
	arangod/Aql/OptimizerRules.cpp