Tests: Overlays
First tests to a Module. Input events tested.
Email Module fully tested.
Hook up the TOS/PP agreements.

* fxam_ui.js - Ensure transitions work for panels that do not have JS modules.
* fxam_navigation.js - Ensure initialization, back work for panels that do not have JS modules.
* Extract function refactorings in fxam_navigation.js & fxam_ui.js for readability
* In templates, convert h2 to h3 to go along with h3 CSS changes in #23
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.

Conflicts:
	apps/system/fxa/js/screens/fxam_enter_email.js
replaced sub/sub with calling a refresh function
Hide irrelevant items on keyboard input
enable / disable nav buttons
progress from states