Merge branch '205-document-elphy' into 'feature'

src/CardiacInterpolation.cpp

src/MainCardMech.cpp

src/MainCardMech.hpp

src/MainElphy.cpp

src/cellmodels/MBeelerReuter.cpp

src/cellmodels/MBeelerReuter.hpp

src/cellmodels/MCellModel.cpp

src/cellmodels/MCellModel.hpp

src/cellmodels/solvers/MElphySolver.cpp

src/cellmodels/solvers/MTensionSolver.cpp

src/cellmodels/solvers/MTensionSolver.hpp

src/coupled/MainCoupled.cpp

src/coupled/MainCoupled.hpp

src/coupled/problem/CoupledProblem.hpp

src/elasticity/MainElasticity.cpp

src/elasticity/MainElasticity.hpp

src/elasticity/assemble/DGElasticity.cpp

src/elasticity/assemble/EGElasticity.cpp

src/elasticity/data_processing/DisplacementLogger.cpp

src/elasticity/data_processing/VectorLogger.cpp