Removed most of absolute_import imports

Should be unneeded with Python 2.7 and up.
Added some unicode_literals along the way.
Fixed #20823 -- Typo in docs/ref/forms/validation.txt
Fixed #20785 -- Corrected exception caught for Oracle LIKE operator detection

The code that tests to see which LIKE expressions to use now runs
using non-error-wrapped cursor, so cx_Oracle exceptions need to be caught
rather than Django DatabaseErrors.

Thanks Trac user ludo for report and initial patch.
Fixed #19082 -- Enabled admin field pre-population for existing objects.
Thanks to msaelices and d1ffuz0r for the initial patch and tests.
Updated some minified admin javascript files.
Doc tweaks for html_message parameter to send_mail(); refs #20817
Fixed #19877 -- Added `--no-color` option to `BaseCommand` to avoid using output styles.
Fixed a test that could fail depending on PASSWORD_HASHERS.

Thanks Claude. Refs #20760.
Fixed a test that depended on the DB backend; refs #19877. Thanks Loic.
Removed part of a test that doesn't work on Jenkins; refs #19877.
Updated flatpages tests to override CSRF_FAILURE_VIEW.
Added support for IPython.start_ipython in shell

IPython 1.0 introduces an actual stable public API function
for starting a normal (non-embedded) IPython session.

This is an official public API, which is promised to survive implementation changes.
Fixed #10491 -- Allowed passing lazy objects to HttpResponseRedirect.

Thanks liangent for the report.
Fixed #20806 -- Cached loader caches find_template

The cached template loader should cache find_template in addition to
load_template.