Design cleanup

Introduces a lot of small visual + functional cleanup.

- No more truncating on data details
- Better state handling in places UI.
- Cleaner `#layers` panel header.
- Cleaner source/styling listings
- Simpler source UI changing
- Better validation in source change form (Allows for spaces between comma separated IDs, works for local sources)

TODO 
- [x] Fix old tests
- [x] Write new tests for modified source change UI