Merge branch '01-hookup-to-fte' into all-fxa-things
Merge branch '02-hookup-tos-pp' into all-fxa-things
Too many changes?

Contains:

- All panels changed by hashchange
- CSS back to being flexbox based
- only initialize panels / panel javascript once
- pub/sub for params shared between panels (Could use DOM listener
  instead)
- Navigation back to the panels

Broke:
- Not fixed next / prev enabled / disabled (should be handled within the
  panel)
- Some duplication / oddness left when changing to self contained
  panels.