Fixed #18026 -- Don't return an anonymous dict if extra_data in storage is empty.
Fixed #19024 -- Corrected form wizard docs for get_form_prefix.
Return namedtuple from get_table_description

We don't make use of it currently to not break third-party db
backends.
Fixed #17574 -- Implemented missing get_key_columns in PostgreSQL backend
Fixed #14633 - Organized settings reference docs and added a topical index.

Thanks Gabriel Hurley for the original idea
and adamv for the draft patch.
Fixed typo in file storage docs.

Thanks Jørgen Abrahamsen.
Added details on minified jQuery and DEBUG mode for contrib.admin.

Thanks Daniele Procida.
Merge remote-tracking branch 'upstream/master'