Complete refactor for SPA support

[cyberbit]

The entire site is a SPA now, so the current content script system has to be re-written. This will probably be done as a complete overhaul (again). This will be marked on the v3.0 roadmap.

:(

• [ ] Make content scripts fire on history event changes
• [ ] Add watchlist buttons
• [ ] Fix styles in badge popup
• [ ] Fix API calls that require CSRF tokens