Fixed #19571 -- Updated runserver output in the tutorial
Created special PostgreSQL text indexes when unique is True

Refs #19441.
Fixed typo in 1.5 release notes; thanks Jonas Obrist.
Fixed #16759 -- Remove use of __deepcopy__ in qs.clone()

The original problem was that queryset cloning was really expensive
when filtering with F() clauses. The __deepcopy__ went too deep copying
_meta attributes of the models used. To fix this the use of
__deepcopy__ in qs cloning was removed.

This commit results in some speed improvements across the djangobench
benchmark suite. Most query_* tests are 20-30% faster, save() is 50%
faster and finally complex filtering situations can see 2x to order
of magnitude improvments.

Thanks to Suor, Alex and lrekucki for valuable feedback.
Updated deprecated test assertions
Fixed #17541 -- Fixed non-saved/nullable fk querying
Fixed #19576 -- Use `six.with_metaclass` uniformously accross code base.
Fixed #19555 - Removed '2012' from tutorial 1.

Thanks rodrigorosa.lg and others for the report.
Added sphinx substitutions in place of hardcoded version numbers.

Refs #19571