Updated docs following deprecation of django.views.defaults.shortcut

Follows 3f2befc
Fixed some ReST errors regarding backticks
Added release date to 1.5 release notes.

Forwardport of 61283a8208 from 1.5.x
Regression test and patch for ticket #20924.
Fixed #20891 -- Removed part of the tutorial that requires pytz

Thanks AtomicSpark for the report.
Fixed #20895 -- Made check management command warn if a BooleanField does not have a default value

Thanks to Collin Anderson for the suggestion and Tim Graham for
reviewing the patch.
Combine consecutive with statements

Python 2.7 allows to combine several 'with' instructions.
Fixed #20829 -- Skip postgis metadata tables with introspection
Remove the last FIXME from the howto-release-Django doc.
Update LazyObject method proxy declarations to simpler form.
Merge pull request #1479 from nickbruun/ticket_20924

Proxy __len__ and __contains__ for LazyObject
Some code simplification
Made Model.__eq__ consider proxy models equivalent

Fixed #11892, fixed #16458, fixed #14492.
Fixed #20777 -- Admin proxy model deletion regression

Added proxy_models tests by Harm Geerts <github@geertswei.nl>.
Fixed #12567 -- Incorrect SQL in model inheritance case

An isnull lookup produced incorrect SQL. This was already fixed
earlier, so only tests added.
PEP 8 cleanup
Fixed #12886 -- aggregation over sliced queryset
Fixed #11881 -- removed junk from aggregation subqueries

There were clauses that weren't needed in the subqueries. These were
ORDER BY, SELECT FOR UPDATE and related selections.
Fixed #12807 -- EmptyResultSet ORed condition

The EmptyResultSet wasn't treated correctly so the end results was
incorrect, too. The bug had been already fixed in master so only tests
added.
Removed versionadded/changed annotations for 1.5