Fixed ticket #21172

LiveServerThread.join() now behaves like threading.Thread.join().
LiveServerThread.terminate() is instead used to ask live http server to
terminate and close.
Merge pull request #1743 from unaizalakain/ticket_21172

Fixed #21172 -- have LiveServerThread follow the semantics of threading.Thread.join()
Fixed #16969 -- Don't connect to named database when possible

Thanks Andreas Pelme for the report and initial patch, and
Aymeric Augustin, Shai Berger and Tim Graham for the reviews.
Removed useless comment. Refs #21172
Don't initialize PostGIS-specific stuff for non-db connections

Refs #16969.
Fixed #21383 -- Added request details in SuspiciousOperation messages
Recommended flake8 to check coding style.
Fixed #21378 -- Updated tutorial02 for how to override admin site header.
Fixed versionadded misuse in the admin documentation.
flake8 fix
Fixed doc typo.
Fixed #21398 -- Fixed BCryptSHA256PasswordHasher with py-bcrypt and Python 3.

Thanks arjan at anymore.nl for the report.
Fixed spelling of compatibility.
Fixed #14800 -- Suppressed WSGIRequestHandler message filtering

Filtering out static file requests in runserver has been judged
arbitrary and can hide some debugging-related activity.
Thanks Roy Smith for the report and Aymeric Augustin for the
review.
Fixed #21372 -- Corrected docs regarding translating LANGUAGES.

Corrected LANGUAGES documentation on how to translate language
names. Now using django.utils.translation.ugettext_lazy instead
of a dummy gettext() function.

Thanks to Salvatore for the report.
Fixed typo in tutorial 2; refs #21418.
Add thread-safe CacheHandler
Documentation tweaks
Remove all uses of get_cache
And the rest of them