Renamed elphy solver methods

src/coupled/solvers/CellModelSolver.cpp

src/coupled/solvers/SegregatedSolver.cpp

src/electrophysiology/MainMonodomain.cpp

src/electrophysiology/MainOneCell.cpp

src/electrophysiology/solvers/DiffusionSolver.cpp

src/electrophysiology/solvers/DiffusionSolver.hpp

src/electrophysiology/solvers/ElphySolver.cpp

src/electrophysiology/solvers/ElphySolver.hpp

src/electrophysiology/solvers/LinearImplicitSolver.cpp

src/electrophysiology/solvers/LinearImplicitSolver.hpp

src/electrophysiology/solvers/SplittingSolver.hpp

test/coupled/TestCoupledConsistency.cpp