Improve first-time setup and observation download

[JWCook]

• [x] re-run db setup if the app has been updated to a different version
• [x] add option to download missing taxonomy data (at least via CLI)
• [ ] First-time setup: load UI first, then show progress bar
• [ ] Initial user observation download: populate first page in UI, then download the rest
• [ ] Initial user observation download and incremental updates: add correct progress bar increments
  • [ ] Initialize with total # of observations (available after first request)
  • [ ] Update in per_page increments
  • [ ] Disable pagination buttons until more pages are loaded