Uisng CellModel instead of ElphyModel

src/cellmodels/MCellModel.hpp

src/cellmodels/solvers/MElphySolver.cpp

src/cellmodels/solvers/MElphySolver.hpp

src/electrophysiology/assemble/IElphyAssemble.cpp

src/electrophysiology/assemble/IElphyAssemble.hpp

src/electrophysiology/assemble/Monodomain.cpp

src/electrophysiology/assemble/Monodomain.hpp

src/electrophysiology/solvers/ElphySolver.cpp

src/electrophysiology/solvers/ElphySolver.hpp

src/electrophysiology/solvers/LinearImplicitSolver.cpp

src/electrophysiology/solvers/LinearImplicitSolver.hpp