Merge branch 'revisions' of geraldine.fjfi.cvut.cz:/local/projects/tnl/tnl into revisions

Conflicts:
	src/functions/tnlOperatorFunction.h
	src/operators/tnlFunctionInverseOperator.h
	src/operators/tnlOperator.h
	src/operators/tnlOperatorComposition.h
	tests/unit-tests/operators/diffusion/CMakeLists.txt