Spruce-up the interface (accordions, TPMA-category dropdown, spinners, bugfixes)

[matt-dray]

These is a 'tweak the UI' special and encompasses many small changes to improve look and feel. These are all part of milestone v0.3.1.

• Close Alphabetise LAs #55 (adjusted raw data to order by LA name, not code).
• Close Replace NaN in summary tables #56 (returned NULL if the procedures/diagnoses are empty, which now activates validate(need()) correctly).
• Close Use linewidth, not size #57 (fixed warning in geom_segment()).
• Close Add loading spinners #27 (added spinners to all outputs).
• Close Add basic categorisation to select TPMAs #60 (added new activity-type selectInput() to whittle down the TPMA dropdown selections).
• Close Use accordions in the sidebar, open when data loads #61 (added accordions to the sidebar, made them expand only when data has loaded).
• Prepared for Add bookmarks #59 (added server-based bookmarking).

The app has been redeployed with these updates. Happy to chat it through, of course.

[matt-dray]

Originally this closed #59, but then I realised bookmarking is more complicated than I thought when you have modules. Removed the button for now. Edit: and redeployed now.

[matt-dray]

Pixelated screenshots of the app after this PR was merged. Click to expand to full size.

With an NHP scheme:

With an LA: