[ML] Const iterator access to mesh's elements.
[ML] Add elments iterator to MeshSubset.
[ML] Add mesh subsets iterator in MeshSubsets.
Correct doxygen paths for Documentation/ dir.
Doxygen: Correct input paths.
Add/correct missing \f$ in doxygen comments.
Update doxygen config for 1.8.8.
Merge branch 'CorrectionsToDoxygen' into develop
[AL] Temporarily disable constructor for rows != colmuns.

This is used for parallel meshes and has to be implemented later.
Now it's not even tested.

In LocalToGlobalIndexMap save a copy of _rows.
And the _columns are the same as _rows being a reference.
[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.
Merge branch 'RefactorDofTableConstruction' into develop