Finished up the common API

I'm very glad to be finished with the common API for now. I'll just note that this is the client API for the DRM, though the methods apply to COODBMS's RolonicElements and many of the methods also apply to the CowDb handles and elements.

However, there are now several changes that I am aware of that need to be made to the model. So I expect to be working on the model tomorrow.