[ML] Removed unused variables.
Merge pull request #485 from TomFischer/FixWarning

[ML] Removed unused variables.
[A] Fix infinite recursion in findMeshByName.
Merge pull request #489 from endJunction/FixInfiniteRecursion

[A] Fix infinite recursion in findMeshByName.
[PL] Add mesh subset to initialize().
[PL] Initialize MeshSubsets and MeshComponentMap.
[PL] Rename mesh_items_all_nodes; items->subset.
[PL] Add destructor for GroundwaterFlowProcess.
[PL] Move mesh_component_map to class variables.

...from the initialize().
Also delete it in the dtor.
[PL] Add createDofMap() in Process.
[PL] Use number of node's DOF in createDOFMap().
[PL] Remove MeshComponentMap include from GW.
[PL] Add dof_map to GroundwaterFlow.
[PL] Empty solve().
[PL] Add empty GroundWaterflowFEM.