Simplified admin delete confirmation templates using {% elif %}.

Thanks jonash for the initial patch; refs #20133.
Fixed flake8 warning.
Improved formatting of deconstruct() docs.
Fixed #20368 -- Made TECHNICAL_500 more robust against bad input.

This limits large variables and avoids non-utf-8 in the TECHNICAL_500 output.
Removed tabs from an admin CSS file.
Refs #23276 -- Added missing url() in some places.
Fixed #23283 -- Added default=False to BooleanField's in the docs.

Thanks Baptiste for the suggestion.
Fixed #22646: Added support for the MySQL ssl-ca option to dbshell.
Fixed #21603 (again) -- Made a raw query in a test Oracle-compliant
Fixed #18767 -- Fixed admin calendar for other locales than English.

Refactored openCalendar function from DateTimeShortcuts.js. Now, when
entered manually in the input field, the date will show up correctly on
the calendar for locales that don't use "-" for separator.

Thanks charettes for revivew and Alexey Boriskin for some of the patch.