Work done:
Create new template class Maxwell_DG<Dim, Order_poly,Order_geo>
Add methods : - assemble_LHS (mass matrix)
              - assemble_RHS (flux term)
              - solve (linear system)
Comments :
-> assemble_rhs :: Compute 2D Flux for Maxwell in TM mode
-> code run with mpi (thanks to extended dof table, lose lot of time on it..;) )
-> splitting into .hpp file and .main

Start working on :
-> use mpi timer
-> time marching scheme RK4 (interface with petsc ?)
-> study theory (flux form and equation) for 3D extension