[PL] Move createDofMap to AssemblerLib.
[AL] Store mesh component map and subsets locally.

GW: Update construction of local_to_global_map.
[AL] Pass only size to createVector/Matrix.

In the vector matrix builder only size is used.
[AL] Add LocalToGlobalIndexMap::dofSize().
[PL] GW: Change comments on mesh subsets creation.
[T] Save local_to_global_map.

Otherwise there is a reference to temporary.
[T] Update AssemblerLib tests for new LocalToGlobalMap.
[ML] MeshComponentMap: Remove unused include.
[AL] Extract private appendGlobalIndices().