Django-spectator

- Undid/simplified some of the previous date-related settings; needs more thought.

Core

- Remove leading `www.` from visible display of domains when URLizing them.
- Better handle default settings.

Reading

- Add optional settings to customise the format of dates when displaying Readings.
- Stop possibility of a Publication appearing more than once when listing Publications being read on a specific day.
- Order in-progress Publications by when they were started to be read.

Events

- Turn Exhibitions into a new kind of Work:
- Renamed `"exhibition"` Events to be `"museum"` (Museum/Gallery) Events.
- Added `"exhibition"` as a new Work kind.
- Added a migration to add an Exhibition Work to every Museum/Gallery Event, and move any Creator(s) over to that Work.
- Add optional settings to customise the format of Event dates in templates.
- Display the number of Events on a Venue detail page.

- Add `Creator.get_events()` method for more accurate counting.
- Fix bug with counting Events or Works multiple times when counting a Creator's Events/Works and they had more than one role on an Event/Work.
- Add counts of Venues and Movies/Plays/etc on their list pages.

- Tweaked `spectator_core/includes/chart.html` template to allow multiple objects per chart position.

- Added template tags for getting the Creators with the most Works.

- Added several manager methods for getting Creators, Venues and Works ordered by things such as most-read, most-visited, most-seen, etc.
- Added template tags for displaying charts of the above (and used them in templates).
- Added `annual_reading_counts_card` template tag for displaying a table of how many books and/or periodicals were finished each year.
- A few template fixes/tweaks.