New spreadsheet model interface

The new spreadsheet model is ready to be used. It should support the same features than the old one and has a new value interpretation and function lookup implemented. ASMInterfaceTest demonstrates the application of the model.

To avoid conflicts I added the new messages at the end of the common.proto file. I hope that the new structure is more simple than the old one.

I would be happy about some feedback concerning the ontology linking and model in general. 

A serialisation is not implemented, because I would like feedback first.