added case to cast down MutableVerticalTable
Merge branch 'feature/mtv_op' of https://github.com/bastih/hyrise into feature/nested_radix_joins
Merge remote-tracking branch 'upstream/master' into feature/nested_radix_joins
patch for gcc 4.6
added Exception for case that get a MutableVerticalTable that does not consist of PointerCalculators as input
Merge branch 'feature/nested_radix_joins' of https://github.com/JWUST/hyrise into JWUST-feature/nested_radix_joins

Conflicts:
	src/lib/taskscheduler/AbstractTaskQueue.h