Moved ServerHandler helper class to tests.

It has been only used in the builtin_servers tests since Django 1.4.
Fixed #22626 -- Allow BinaryField defaults with SQlite.

Also fixes a slight issue in sqlite3.schema._remake_table where
default values where quoted with "column name" quoting rules.

Reference for quoting: http://www.sqlite.org/lang_expr.html

Thanks Shai Berger for the review. Refs #22424.
Fixed #22421 -- Regression in fixtures loading.

Loading fixtures were failing since the refactoring in 244e2b71f5 for
inheritance setups where the chain contains abstract models and the
root ancestor contains a M2M relation.

Thanks Stanislas Guerra for the report.

Refs #20946.
Fixed #22424 -- Fixed handling of default values for TextField/BinaryField on MySQL.

Thanks syphar for the review and suggestions.
Failing testcases for #22649.
Fixed #22661 -- Move makemigrations tests to the proper class
Merge pull request #2688 from whoshuu/22661

Fixed #22661 -- Move makemigrations tests to the proper class
Removed unused translations in auth tests
Fixed #22645: Allow apps with no models module to still have migrations
Add feature for implied null (needed for Firebird backend)
Merge pull request #2634 from loic/ticket22424

Fixed #22424 -- MySQL doesn't accept migrations' one-off default values ...
Fixed #22649: Beefed up quote_value
Fixed #22432: SQLite M2M repointing now works. Thanks to xelnor.
Revert "Fixed #22645: Allow apps with no models module to still have migrations"

This reverts commit a4737bf6ae36a5f1cb29f2232f6deeff084fabff.
Fixed #22557 -- ManifestStaticFilesStorage did not cleanup deleted files.

When using ManifestStaticFilesStorage, deleted static files would be
correctly cleaned up by "collectstatic --clear", but the manifest file
would still contain the stale entries.

Thanks to tedtieken for the report
replaced occurrences of master/slave terminology with leader/follower
Merge pull request #2692 from fcurella/patch-5

#22667 replaced occurrences of master/slave terminology with leader/follower
Fixed #22650 -- Fixed regression on prefetch_related.

Regression from f51c1f59 when using select_related then prefetch_related
on the reverse side of an O2O:

Author.objects.select_related('bio').prefetch_related('bio__books')

Thanks Aymeric Augustin for the report and tests. Refs #17001.
Fixed the ordering of prefetch lookups so that latter lookups can refer to former lookups.

Thanks Anssi Kääriäinen and Tim Graham for the reviews. Refs #17001 and #22650.
Fixed unused import.