adding forgotten file
new classes for session/connection separation
work in progress; basic things working but we still need to share model templates
IMPORTANT: very large refactoring so that OOOR::Base uses sessions (multiple session per user eventually as OpenERP v8 web is designed for) and also introduce the concept of ModelTemplate which is meta-data that is shared when possible using ModelRegistryHandler
added a few tests for multi-sessions; more to come