Merge branch 'distributed_field' into 'master'

src/common/GmshFem.cpp

src/common/GmshFem.h

src/common/gmshfemDefines.h.in

src/field/CMakeLists.txt

src/field/DistributedField.cpp

src/field/DistributedField.h

src/field/FieldInterface.cpp

src/field/FieldInterface.h

src/problem/Formulation.cpp

src/problem/Formulation.h

src/system/CMakeLists.txt

src/system/DistributedContext.cpp

src/system/DistributedContext.h

src/system/Solver.cpp

src/system/Solver.h

src/system/VectorFactory.h