Started work on coupled problems

.gitignore

conf/coupled/cellmodels.conf

conf/m++.conf

src/coupled/CMakeLists.txt

src/coupled/problem/CMakeLists.txt

src/coupled/problem/ICoupledProblem.hpp

src/coupled/problem/PhysiologicalProblems.cpp

src/coupled/problem/PhysiologicalProblems.hpp

src/elasticity/problem/VentricleProblems.hpp