- added a flag to relation(), eagerload(), and eagerload_all()

- added a flag to relation(), eagerload(), and eagerload_all()
called 'innerjoin'.  Specify `True` or `False` to control
whether an eager join is constructed as an INNER or OUTER
join.   Default is `False` as always.   The mapper options
will override whichever setting is specified on relation().
Should generally be set for many-to-one, not nullable
foreign key relations to allow improved join performance.
[ticket:1544]