Better migration docs for get_query_set -> get_queryset

This way they won't need to fix things again when get_query_set disappears
Removed unused variable django.http.request.absolute_http_url_re
Simplified get_version() in django/__init__.py

Thanks Luke Plant for the report.
Moved release note for refs #21281 from "deprecation" to "backwards incompatible".
Fixed spelling in docs/ref/django-admin.txt.
Added deprecation of template dirs parameter to timeline.
Fixed #23543 -- Added docs on testing management command output.
Further fixes to the migration notes for get_query_set

This rename is very tricky for the case of subclasses which define
get_query_set and haven't been updated yet, which applies to all projects in
the form of RelatedManager from Django 1.5.
Fixed typo in django/utils/decorators.py comment.
Updated testing documentation following 498ae3a36069e2d

- commit/rollback are no longer replaced by nop
- the warning about not using TestCase when testing transactional
  behavior belongs to TestCase section, not TransactionTestCase
Fixed #13694 -- Made SafeMIMEText's constructor compatible with MIMEText.
Removed workaround for lack of os.getpid() in Jython.

The Jython bug was fixed in http://bugs.jython.org/issue1518
(tested on Jython 2.7b3); also updated make_msgid() to be more like
the version in Python 3.2+; refs #23905.

Thanks Simon Charette for testing and review.
Fixed #23888 -- Fixed crash in File.__repr__() when name contains unicode.
Fixed #23907 -- Added admin.site.register in tutorial 2 for consistency.
Changed test_runner imports to name objects imported from test.runner.
Improved line breaking in runtests docs.
Fixed #23742 -- Added an option to reverse tests order.

This is useful for debugging side effects affecting tests that
are usually executed before a given test. Full suite and pair
tests sort cases more or less deterministically, thus some test
cross-dependencies are easier to reveal by reversing the order.

Thanks Preston Timmons for the review.