Fixed the PostGIS circular imports caused by 1506c71a95.

Thanks to @loic for the help and @timgraham for the review.

refs #12030.
Fixed #22114 -- Stopped adding trailing slashes in URLField.to_python

Thanks coredumperror at gmail.com for the report and Tim Graham
for the review.
Forgotten slash removal in d320863878
Add a useful stacklevel to some RemovedInDjango19Warnings
Skipped a test that errors rather than marked it as an expectedFailure.

The test throws an error which Python 3.4 doesn't seem to catch as an
expectedFailure.

refs 7476d96f83a004d674244aeb7a66289035427396
Fixed a deprecation warning on Python 3.
Fixed #21941 -- Documented the kwargs param of django.conf.urls.url().

Thanks cjerdonek for the report.
Added Python 3.4 support notes.
Fixed a deprecation warning with the HTMLParser safe argument.

refs 6ca6c36f82b97eafeada61384b2e2f1d0587da86
Skipped JavascriptI18nTests if Firefox isn't properly configured.

Code borrowed from django.contrib.admin.tests. Without this, the class can
throw an exception with something like "The browser appears to have exited
before we could connect. The output was: Error: no display specified"
Corrected deprecation warnings.
Fixed #22306 -- Deprecated future versions of cycle and firstof template tags.
Fixed #22250 -- regression in gis compiler for non-concrete fields

Thanks to gwahl@fusionbox.com for the report.
Confirmed GEOS 3.4 support
Confirmed Spatialite 4 support
Added note in geo library docs
Dropped support for GEOS 3.1
Dropped support for GDAL 1.6
Removed unused imports.
Fixed #22329 -- Used label_tag() in some admin auth templates.

refs #17922.