Use local assets over external ones [58158124]

* Remove links to the following external assets:
  * New transport font
  * HTML5 shiv
  * Favicon
  * App icons and open graph images
* Use local favicon and HTML5 shiv
* Update styles to use Gill Sans instead of New Transport
* Remove duplicate meta viewport tag
* Brings app styles further inline with older admin apps (eg publisher), holds off on any potential updates to admin app styles