Added support for new :attr:`.Session.info` attribute to
:class:`.scoped_session`.
- The ``viewonly`` flag on :func:`.relationship` will now prevent
attribute history from being written on behalf of the target attribute.
This has the effect of the object not being written to the
Session.dirty list if it is mutated.  Previously, the object would
be present in Session.dirty, but no change would take place on behalf
of the modified attribute during flush.   The attribute still emits
events such as backref events and user-defined events and will still
receive mutations from backrefs. [ticket:2833]
- The :class:`.RowProxy` object is now sortable in Python as a regular
tuple is; this is accomplished via ensuring tuple() conversion on
both sides within the ``__eq__()`` method as well as
the addition of a ``__lt__()`` method. [ticket:2848]
break up behavioral changes into ORM and Core