Share & Remix panel updates.

This is the little panel that slides up with the orange tab.

Changes:
* Added QR code for sharing
* Added Email Remix link feature
* Added Email to Share feature
* Removed 'Install App' button when app is already installed
* Remix button opens a Email Remix popup when not on desktop

Tested on:
* Desktop Chrome
* Desktop FF
* Firefox OS
* Firefox on Android

this is quite a lot of code, can we put this in its own file instead and `src=...` link it in?