Procedures to load information about current library as a map

Various procedures have been added to load the information about the current library, classes and attributes into a map.

The main procedure is MMATRT_GET_CURRENT_METAMODEL mLibrary:reference which creates a description of the currently loaded library as an ADOxx map. The structure of the map is similar to how a library is presented in the ADOxx Development Toolkit, trying to use the same names where possible.