Fixed documentation of disable_constraint_checking

The docstring and base implementation of disable_constraint_checking do not indicate that a return value is expected for proper behavior.
Added clarification to the docs, pointing out that unique_for_date only considers the date portion of DateTime fields.
Remove outdated ForeignKey manager documentation.
Fixed #20354 -- `makemessages` no longer crashes with `UnicodeDecodeError`

Handle the `UnicodeDecodeError` exception, send a warning to `stdout` with the
file name and location, and continue processing other files.
Python 2.5 is not relevant to master.
Fixed inconsistent punctuation in tutorial 5.
Fixed Sphinx error in tutorial 1.
Remove unnecessary check on __set__ parameters.
Fixed #20256 -- Corrected startproject --template help text

Thanks n0nam3 for the patch.
Fixed test failures on MySQL.

Some tests failed when the time zone definitions were loaded in MySQL
and pytz wasn't installed. This setup isn't supported.
Fixed #20025 -- Pointed to a MySQLdb fork for Python 3.

Made a few minor compatibility adjustments.
[py3] Stopped iterating on exceptions. Refs #20025.
Marked tests of BinaryFields as expected failures on MySQL and Python 3.

Current ports of MySQLdb are very buggy in this area.
Added an HTTP status code to Django's WSGI application that was missing (reason unknown).
Marked a test as an expected failure on MySQL and Python 3.2.

This test hits a bug in current ports of MySQLdb.
Removed fragile admin validation of fields on ModelForm

Refs #19445
Removed some failing tests missed in 1556b1c3b7a18cadf4d66d2ab6301d7fe8646ba5
Merge pull request #1049 from mfogel/remove-unescessary-parameter-checks

Remove unnecessary check on __set__ parameters.
Fixed #20215 -- Disabled persistent connections by default.
Removed a test that didn't make sense; code could never be called the way the test was written.