add sane_multi_rowcount requirement, as pg8000 doesn't do "multi" row count.

sqlalchemy/orm, sqlalchemy/event, sqlalchemy/testing

- edit strategies.py to conform

the "outer join" propagation along a chain of joined eager loads
would incorrectly convert an "inner join" along a sibling join path
into an outer join as well, when only descendant paths should be
receiving the "outer join" propagation; additionally, fixed related
issue where "nested" join propagation would take place inappropriately
between two sibling join paths.

this is accomplished by re-introducing the removed flag "allow_innerjoin",
now inverted and named "chained_from_outerjoin".  Propagating this flag
allows us to know when we have encountered an outerjoin along a load
path, without confusing it for state obtained from a sibling path.

fixes #3131
ref #2976

:meth:`.Query.select_from` method no longer set up the "from
entity" of the :class:`.Query` object correctly, so that
subsequent :meth:`.Query.filter_by` or :meth:`.Query.join`
calls would fail to check the appropriate "from" entity when
searching for attributes by string name.
fixes #3083

to get all flake8 passing

updates, and needs to be set to `synchronize_session=False` or
`synchronize_session='fetch'`; this now raises an exception, with a
message to change the synchronize setting.  This will be only a warning
in 0.9.7.  fixes #3117

Typo fixes

primary key change within a savepoint block would not
participate in being restored to their former state (not in
session, in session, previous PK) after the outer transaction
were rolled back. fixes #3108