Modifs to make pugs compile when costo is not found

CMakeLists.txt

cmake/FindParMETIS.cmake

src/language/modules/CouplageModule.cpp

src/language/modules/CouplageModule.hpp

src/language/modules/ModuleRepository.cpp

src/language/modules/SchemeModule.cpp

src/scheme/HyperelasticSolver.cpp

src/scheme/VectorDiamondScheme.cpp

src/utils/Messenger.cpp

src/utils/Messenger.hpp

src/utils/Serializer.cpp

src/utils/Serializer.hpp

src/utils/pugs_config.hpp.in