adds create and get method to orm db class
adds list_users method to orm database
ORM DB class can now:
  -> create and get listings
  -> create and get reservations
  -> create and get reviews
  -> create and get messages
  -> create and get sessions
  -> get a user by session id
Merge branch 'ORM-db' into development

Conflicts:
	spec/db/shared_spec.rb