Addressed inaccuracies in performance docs

* Move the discussion of CachedStaticFilesStorage to the section about
  HTTP. It's really about client-side caching. It doesn't fit with the
  caching utilities from django.utils.functional.

* Tone down the warning against Pypy as per Alex' feedback. It's a valid
  choice for advanced users who are comfortable using a non-standard
  stack.

* Generally reworded the 'Using different versions of available software'
  section.

* Some other minor adjustments to the document.
Merge pull request #1655 from evildmp/ticket_20877_work_in_progress

Addressed inaccuracies in performance docs
Ensured that explicit time zones are rejected by forms.

Refs #19371.
Correct very minor typo

Just changed as to has.
Merge pull request #1656 from mlissner/patch-1

Correct very minor typo
Ensured that BoundField.as_widget always returns properly localized fields.

This is a follow-up to #18777 which improperly converted to strings in
prepare_value and as such caused regressions like #21074.

Refs #18777, #21074
Fixed #21074 -- Added tests for localized datetime fields.

Fields must render values in the current time zone.

This commit only contains tests because this ticket was just a symptom of
a regression from #18777 that was fixed separately.
Fixed #21137 -- Documented best practice for URLconfs with repeated pattern prefixes.
Partial revert of 165f44aa.

That commit didn't always improve readability.

See discussion on django-developers for details.
Removed a few trailing backslashes.

We have always been at war with trailing backslashes.
Fixed a mistake in my previous commit.
Reference Meta.index_together in DB performance guide.
A few doc additions for changes from d228c1192e.
Fixed #21141 -- Update Sphinx URL
Updated Sphinx URL from http://sphinx.pocoo.org/ to http://sphinx-doc.org/.
Merge pull request #1658 from yokomizor/updated_sphinx_url

Fixed #21141 -- Updated Sphinx URL.
Added docs for changes in commit dd3a883894.

Refs #20693.
Fixed "Address already in use" from liveserver.

Our WSGIServer rewrapped the socket errors from server_bind into
WSGIServerExceptions, which is used later on to provide nicer
error messages in runserver and used by the liveserver to see if
the port is already in use. But wrapping server_bind isn't enough since
it only binds to the socket, socket.listen (which is called from
server_activate) could also raise "Address already in use".

Instead of overriding server_activate too I chose to just catch socket
errors, which seems to make more sense anyways and should be more robust
against changes in wsgiref.
Translated a test to English for consistency.

Also fixed a typo.
Stopped a test from executing queries at the module level.

Currently module level queries are executed against the real database
(specified in NAME) instead of the test database; since it is to late
to fix this for 1.6, we at least ensures stable builds. Refs #21443.
Fixed #21702 -- Added different bullet styles for nested lists.

Thanks moc at mocpa.com for the suggestion.