Stopped branding Python 3 support as experimental.

Forward-port of 0de21a6 from stable/1.6.x.
Bumped minimum Python version requirement to 2.7 in Django 1.7.
Removed some conditional code only needed under Python 2.6.
Fixed #20659 -- Fixed PublisherDetail in CBV topic documentation.

Thanks to tudor.prodan, susan, and Tim Graham for the report and reviews.
Fixed #20680 -- Deprecated django.utils.unittest.

Refs #19204.
Stopped using django.utils.unittest in the test suite.

Refs #20680.
Updated tests for deprecation of Option.get_(add|change|delete)_permission.

refs #20642.
Fixed a couple form/formset deprecation warnings in tests.
Removed tests for django.utils.unittest vs. unittest.

Silenced warnings caused by the deprecation of django.utils.unittest.

Thanks Preston Timmons and Carl Meyer for their advice.

Fixed #20680.
This doesn't need to be a package any more.

Refs #20680.
Fixed a few more imports of django.utils.unittest.

One import per line please! Refs #20680.
Deprecated django.utils.dictconfig.

The module still exists for whoever uses it in its current state, but it
isn't imported by Django anywhere.
Reflected the new default value of LOGGING_CONFIG in docs.
Relied on NullHandler from the logging stdlib module.
Merge branch 'master' into schema-alteration
Fix M2M interaction with transactions
Add unique_together altering operation
Autodetection of unique_together changes
Support for index_together in schema backends
Fix combined alters on PostgreSQL