Removed model_id from Model objects, which in any case in managed by session.  But tests aren't passing; need to investigate further.

Merged in usage of session module global object instead of singleton class; still working through tests

Resolved Session re-initialization issue: Singleton.__call__() recognizes existing instances relative to namespace (model_server.base.session vs. base.session)

Removed test for handling multiple object labels in a patch, now that underlying cause of this problem has been fixed

Moved project file into model.params; removed autogeneration of segmentation model from pixel predictions model