- Added an attribute helper method ``set_committed_value`` in

- Added an attribute helper method ``set_committed_value`` in
sqlalchemy.orm.attributes.  Given an object, attribute name,
and value, will set the value on the object as part of its
"committed" state, i.e. state that is understood to have
been loaded from the database.   Helps with the creation of
homegrown collection loaders and such.
- documented public attributes helper functions.