Add DirichletVectorBoundaryConditionDescriptor

src/scheme/DirichletVectorBoundaryConditionDescriptor.hpp

src/scheme/IBoundaryConditionDescriptor.hpp

...tils/checkpointing/IBoundaryConditionDescriptorHFType.hpp

src/utils/checkpointing/ReadIBoundaryConditionDescriptor.cpp

...utils/checkpointing/WriteIBoundaryConditionDescriptor.cpp

tests/test_checkpointing_IBoundaryConditionDescriptor.cpp