Moab v4.6 changes

uncommented the set_senses error check and added the condition MB_MULTIPLE_ENTITY_HANDLES_FOUND. For the time being I believe this to be ok as this is generally a result of two merged curves referencing the a small surface between them. The sense data for this surface is deleted upon the surface's deletion by the remove_surf_sense_data function I've written in mw_func.cpp so no references to erroneous sense data remain upon the file write. This has been the case for the iter model. 

There is however a case in which curves can share multiple surfaces. However, it shouldn't be one which moab's set_senses has a problem with. I'll be developing a test for this soon.