[2dGWFlow] Add test program body that includes reading of mesh and geo.
Using read fem conditions generating mesh node ids.
Add MeshSubset.
WIP: Added some code for assembling.
Adding element constants (DIM and NPOINTS) as static variables to ShapeQuad4.
Renamed vector mesh_node_ids -> bc_mesh_node_ids.
Added includes for assembly.
[WIP] Try to implement local assembler.
[WIP] Using LocalGWAssembler in GlobalAssembler.
[WIP] Next step is applying BC to sys. of lin. eq.
Reduce debug output (commenting).
Add static and dynamic size eigen matrices types.
Destroy vec_comp_dis at end of program.
Add a LIS global matrix version parallel to DenseMatrix.
Add preprocessor switch LIS/DenseMatrix.
Store bc values in vector and applying to lin eq.
Removed unnecessary matrix in LocalGWAssembler.
Add vector of ShapeMatrices.
Pass ShapeMatrix to LocalAssembler::operator().

Remove local variable.
Fill the vector of shape matrices with FeQuad4 shape matrices.

The number of entries of vector shape_matrix_vec equals the number of mesh elements.
The i-th entry of shape_matrix_vec is associated with the i-th mesh element.