Fixed #19945 -- Fixed default User model Meta inheritance.

Updated default User model Meta class to extend AbstractUser Meta
where translated verbose_name and verbose_name_plural are
defined.
Add a BinaryField model field

Thanks Michael Jung, Charl Botha and Florian Apolloner for review
and help on the patch.
Added support for serializing BinaryField
Add introspection support for BinaryField
Reordered methods in database wrappers.

* Grouped related methods together -- with banner comments :/
* Described which methods are intended to be implemented in backends.
* Added docstrings.
* Used the same order in all wrappers.
Fixed #18130 -- Made the isolation level configurable on PostgreSQL.

Thanks limscoder for the report and niwi for the draft patch.
Fixed #19962 - Added a note about SESSION_EXPIRE_AT_BROWSER_CLOSE and browsers that persist sessions.

Thanks David Sanders.
Fixed #19917 -- Added microseconds in default TIME_INPUT_FORMATS

Thanks minddust for the report.
Fixed #16888 -- Added microseconds in localized input formats
Fixed getting default encoding in get_system_username

Refs #19933.
Fixed #19177 -- Better layout for admin login form field labels.

Thanks goes to void for the comprehensive report, to Pedro Mourelle for
the fix and to Bryan Veloso, Łukasz Rekucki and Claude Paroz for the
review.

This fix includes the following changes:

* Modified layout to top-aligned labels.
* Added 'air' for inputs (the padding was really needed there.). It
  adjust good to zoom in/out.
* Removed float attributes from label and inputs in login form.
* Removed useless text-align property.
Removed unnecessary imports.
Fix Typo explicitly. Fixes #19971
Fixed #19942 -- Decoded errors coming from Popen commands

Thanks Aymeric Augustin for reporting the issue.
Merge pull request #877 from tcarlander/master

Fixed #19971 -- Typo in CBV docs.
Fixed #19915 - Made blocktrans tag honor TEMPLATE_STRING_IF_INVALID.

Thanks Natalia Bidart for the report and Matías Bordese for the fix.
Release notes blurb for 804366327d728d23a9f7a25ff77a6eed3c9f9323.
Removed mentions of regressiontests.
Removed mentions of modeltests.
Merge pull request #871 from matiasb/ticket_19945

Fixed #19945 -- Fixed default User model Meta inheritance.