Fixed a test isolation issue. Refs #17062.

This test could change settings.DATABASES['default']['TIME_ZONE'] and
didn't restore the previous value.
Fixed #21452 -- Non-autocommit connections to PostgreSQL.

When settings.DATABASES['default']['AUTOCOMMIT'] = False, the connection
wasn't in autocommit mode but Django pretended it was.

Thanks Anssi for analysing this issue.

Refs #17062.
Added license info for the weakref backports
Merge pull request #2163 from apollo13/signals

Signals
Fixed flake8 issues.
Fixed #21453 -- Enabled autocommit before calling init_connection_state.

Also ensured the transaction state is clean on Oracle while I was there.

This change cannot be backported to 1.6 because it's
backwards-incompatible for custom database backends.
Restored a test broken by overzealous PEP8 cleanup
Fixed a test that was failing with PostGIS.

Fixed #21452 again.

Forward-port of 18d75e07 from stable/1.6.x.
Used a regular lock for app registry population.

Since the app registry is always populated before the first request is
processed, the situation described in #18251 for the old app cache
cannot happen any more.

Refs #18251, #21628.
Fixed #21477 -- Renamed db to using in pre/post_migrate signals.
Fixed #21770 -- Updated autocomplete for app-loading.

Thanks dfunckt for the report.
Add further workarounds for HTMLParser with Python 3.4.

Python 3.5 will change the default value of convert_charrefs, so 3.4
gives warnings if it's not present. This is slightly technical as 2.7
doesn't have the kwarg. Thankfully, we already have a bunch of
workarounds for different versions.
Undelete the `return True` removed in 4e0a2fe.

This is quite important otherwise we don't close our connections to the
SMTP server.
Be more careful about closing connections in mail tests.
Negligible change to my bio in docs/internals/committers.txt
Removed BDFLs section from docs/internals/committers.txt
Removed BDFL stuff from docs/internals/contributing/bugs-and-features.txt
Remove unneded open(.., 'U') when on python 3.

Universal newlines is enabled by default on py3, and the usage of 'U' is
deprecated in py3.4.
Fixed #21774 -- Isolate all test urls from eachother.

This (nearly) completes the work to isolate all the test modules from
each other. This is now more important as importing models from another
module will case PendingDeprecationWarnings if those modules are not in
INSTALLED_APPS. The only remaining obvious dependencies are:

- d.c.auth depends on d.c.admin (because of the is_admin flag to some
  views), but this is not so important and d.c.admin is in
  always_installed_apps
- test_client_regress depends on test_client. Eventually these should
  become a single module, as the split serves no useful purpose.
Fixed typo in comment.