Added some more list operations.
Added <, <= operators to nvect (useful for bounding box calculations).
Fixed mistake in last commit.
Fixed few things with vect.hpp and moved non-template << operator for lists::end_element out of the header file and into a .cpp file.
Added serialize/deserialize methods for vector in vect.hpp, plus some new named dimensions in dims.hpp.
Made quantity::val private, added access operators for classes which support this.
Added public typdef to quantity; value_type