Added an anchor for django.forms.Form.clean in docs
Improved queryset handling and docs for (Single|Multiple)ObjectMixin.
Merge pull request #1460 from loic/ObjectMixins.get_queryset

Improved queryset handling and docs for (Single|Multiple)ObjectMixin.
Fixed #12288 -- Added unique validation for INSTALLED_APPS
Fixed test failures introduced by #12288
Fixed test failures on Python 3 - refs #12288
Fixed #9057 -- Added default_permissions model meta option.

Thanks hvendelbo for the suggestion and koenb for the draft patch.
SQLite test fix -- refs #9057
Fixed #18356 -- Gave the test client signals.template_rendered call a unique dispatch_uid

This prevents the test client context from being lost when the client
is used in a nested fashion.