Fixed 19949 -- Cached template loader now caches TemplateDoesNotExist

Thanks @timgraham and @jdunck for the code reviews and Kronuz for bug
report and initial patch.
Fixed #20961 -- Fixed HttpResponse default empty content

Thanks epandurski at gmail.com for the report.
Fixed #20814 -- Improved model field accessor clash error messages

Thanks shai for the suggestion.
Ignore coverage HTML report output dir in tests.

Added it to the list of dirs ignored by tests/runtests.py.
Made coverage ignore files without associated source code.

This only affests reporting not data collection and allows coverage.py
to succesfully finish the generation of e.g. the HTML report.

Cases of code whose execution data is collected during the run phase but
for which no associated source code files can be found at the reporting
phase include tests with egg files and Python module files created at
test execution-time.
Fixed typo in docs/topics/conditional-view-processing.txt
Added further fixes, tests for #19949/f33db5a09a.

Thanks Susan Tan. Refs #19949.
Fixed #20972 -- Make messages cookie follow session cookie secure/httponly
Fixed #20693 -- Add timezone support to built-in time filter.

Modified django.utils.dateformat module, moving __init__() method and
timezone-related format methods from DateFormat class to TimeFormat
base class. Modified timezone-related format methods to return an
empty string when timezone is inappropriate for input value.
Merge pull request #1513 from jboecker/typo

Fixed typo in docs/topics/conditional-view-processing.txt
Fixed #20976 -- Fixed labels in migration docs.

Thanks chrismedrela for the report.
Updated instructions for running contrib tests.
Organized 1.7 minor features into subsections.
Fixed #20981 -- Noted the default value of disable_existing_loggers.
Minor spelling correction in ModelForms docs
Merge pull request #1524 from pcx/master

Minor spelling correction in ModelForms docs
Fixed #18171 -- Checked signature of authenticate() to avoid supressing TypeErrors.

The current auth backend code catches TypeError to detect backends that
do not support specified argumetnts. As a result, any TypeErrors raised
within the actual backend code are silenced.

In Python 2.7+ and 3.2+ this can be avoided by using inspect.getcallargs().
With this method, we can test whether arguments match the signature without
actually calling the function.

Thanks David Eyk for the report.
Fixed #20986 -- Enabled SelectDateWidget to use custom months

Reviewed by Trac alias MarkusH.
Fixed #14765 -- Removed unncessary usage of NodeList in ForNode.

Thanks traff and FunkyBob for work on the patch.
Fixed #20983 -- Updated package classifiers in reuseable apps tutorial.

Thanks Cloudream for the report.