Abstract interface for getting mapped command IDs. Command ID mapping means that xSP's own "Names List" command IDs ( constants that are usually defined in a *.hrh file ) are substituted with IDs provided by Extension Manager. This is needed because there may be extensions using same "Names List" command IDs. After the substitution, the original IDs are not valid anymore. Still, in order to allow original "Names List" command IDs usage inside the xSP's own code, MxSPCommandMapper provides the mechanism for retrieving new IDs which correspond to the old original ones and vice versa.