Get rid of `user` property on connections and make minor improvements.
Get rid of `user` property on connections and make minor improvements.

The user property on `Database`'s may be re-introduced as the `role` property,
but will likely to read-only to encourage using a settings context.. However,
not sure that it fits in very well as a "setting".

Minor documentation improvements.

python-postgres/fe,python-postgres/fe