runtime annotation fixes for relationship

runtime annotation fixes for relationship

* derive uselist=False when fwd ref passed to relationship

  This case needs to work whether or not the class name
  is a forward ref.  we dont allow the colleciton to be a
  forward ref so this will work.

* fix issues with MappedCollection

  When using string annotations or __future__.annotations,
  we need to do more parsing in order to get the target
  collection properly

Change-Id: I9e5a1358b62d060a8815826f98190801a9cc0b68