Fixed #20603 -- Made the test suite faster.

By avoiding to run syncdb with the full set of test models.

Thanks Anssi for the idea.
Added missing docs for the checksetup command.
Fixed #20604 - Fixed file example in docs.

Thanks Chris Lasher for the report.
Fixed #20599 -- Changed wording of ValueError raised by _load_library

The _load_library method on BasePasswordHasher turns ImportErrors
into ValueErrors, this masks ImportErrors in the algorithm library.
Changed it to a clearer worded error message that includes
the ImportError string.
Worked around Python 3.3 modified exception repr

Refs #20599.
Fixed #20606 -- Fixed 'for' example in template tag docs

Thanks batisteo for the report.
Adjusted the docs to reflect when the checksetup command was added.
Fixed #20583 -- ORM always uses setup_joins() for join generation

There were a couple of places which used Query.join() directly. By
using setup_joins() in these places the code is more DRY, and in
addition there is no need to directly call field.get_joining_columns()
unless the field is the given join_field from get_path_info(). This
makes it easier to make sure a ForeignObject subclass generates joins
correctly in all cases.
Fixed #20464 -- Added a `total_error_count` method on formsets.

Thanks to frog32 for the report and to Tim Graham for the review.
Fixed #20614 -- Typo in documentation.
Added myself to the commiters list.
Fixed #20615 -- Added trove classifiers for major Python versions.
Refactored ValidationError to allow persisting error params and error codes as the exception bubbles up
Fixed #20199 -- Allow ModelForm fields to override error_messages from model fields
Fixed #20618 -- Fixed regression in `BoundField.label_tag`.
Fixed #20593 -- Allow blank passwords in check_password() and set_password()
Fixed #20079 -- Improve security of password reset tokens
Merge pull request #1280 from erikr/improve-password-reset2

Fixed #20079 -- Improved security of password reset tokens
Fixed #6903 - Preserve admin changelist filters after saving or deleting an object
Merge pull request #1281 from loic/ticket6903

Fixed #6903 - Preserved admin changelist filters.