Django-spectator

- 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.

- Rationalise the usage of 'nav' cards in sidebars.
- Fix the titles and breadcrumbs of the Work List templates.

- Added `title_html` property to `Event` model, which wraps the names of any Works in the title in `<cite></cite>` tags.

- Change theatre and cinema Events' 'kind' fields from 'movie' and 'play' to 'cinema' and 'theatre'.
- Ensure 'sort' fields on models are trimmed to the correct length if greater than their `max_length`.
- Some template tweaks, including to Event list/detail templates' title tags.