CAD12 — altering the use of EntitySeqs to LongSeqs

I suggest altering the use of EntitySeqs to LongSeqs - essentially to use Unique IDs as identifiers. [In places like: Model::delete_entity(), EntityGroup::add_entities(), EntityGroup::remove_entities()] I see there 2 main problems: 1. I don't see that it is really neccesssary to use the (in this case Entity objects) CORBA objects to identify an object. unique_id's could always be used. -> Less traffic and a lot easier to map. Besides: how much sense does the UidUnsupported exception make? unique ids can always be created. 2. The required mapping especially on the server side is somewhat tricky and not the fastest. You would have to map the CORBA objects to the implementation objects. Nasty thing to do.

see below