Collapsing Vector/MultiVector pairs into MultiVec in order to simplify the library in preparation for some upcoming extensions.

--HG--
rename : doc/source/core/dist_multi_vector.rst => doc/source/core/dist_multi_vec.rst
rename : doc/source/core/multi_vector.rst => doc/source/core/multi_vec.rst
rename : include/clique/core/dist_multi_vector_decl.hpp => include/clique/core/dist_multi_vec_decl.hpp
rename : include/clique/core/dist_multi_vector_impl.hpp => include/clique/core/dist_multi_vec_impl.hpp
rename : include/clique/core/multi_vector_decl.hpp => include/clique/core/multi_vec_decl.hpp
rename : include/clique/core/multi_vector_impl.hpp => include/clique/core/multi_vec_impl.hpp
rename : include/clique/numeric/dist_nodal_multi_vector_decl.hpp => include/clique/numeric/dist_nodal_multi_vec_decl.hpp
rename : include/clique/numeric/dist_nodal_multi_vector_impl.hpp => include/clique/numeric/dist_nodal_multi_vec_impl.hpp
rename : tests/NaturalVectorSolve.cpp => tests/NaturalSolve.cpp
rename : tests/SimpleMultiVectorSolve.cpp => tests/SimpleSolve.cpp
rename : tests/MultiVectorSolve.cpp => tests/Solve.cpp