task/us56-introduce-odm -- The Ming Object Document Mapper layer

oct_schema/models/__init__.py
* refactor the schema so that the ODM has a concept of a model.
  The Base() class is now part of the models package

oct_schema/session.py
* refactor the session creation to use the
ming.odm.ThreadLocalODMSession() variant for ODM support
Documentation update
task/us56-integrate-ODM-objects-schema

The OCT Objects collections schema now exists as a specialisation
of the oct_schema.models.base.Base() class
task/us56-document-ODM-model-structure

Documentation around the OCT Objects Collection model