count() here is misleading in that it not only
counts from an arbitrary column in the table, it also
does not make accommodations for DISTINCT, JOIN, etc.
as the ORM-level function does.  Core should not be
attempting to provide a function like this.

Change-Id: I9916fc51ef744389a92c54660ab08e9695b8afc2
Fixes: #3724

we only call upon the history API fully for primary key columns.
We also now skip the whole step of looking at PK columns and using
any history at all if no net changes are detected on the object.

of :ticket:`3060` from verision 0.9.5.  A self-referential relationship
with lazy='dynamic' would raise a TypeError within a flush operation.
fixes #3099

- went through examples/ and cleaned out excess list() calls

on regular append/remove history
- fix the real cause of the original #2637 issue, backrefs call upon
the "pop()" method now which wasn't implemented for Dynamic

the wrong behavior, and for the original #2637 issue we will have to fix the
association proxy, which is #2642

- Fixes to the "dynamic" loader on :func:`.relationship`, includes
that backrefs will work properly even when autoflush is disabled,
history events are more accurate in scenarios where multiple add/remove
of the same object occurs, as can often be the case in conjunction
with the association proxy.  [ticket:2637]

- add "extend()" to AppenderQuery