setup "docs" Collection and move manual sections to docs

This sets up the Docs pages as a _docs Jekyll Collection so nifty Jekyll tricks can be used, like generating the permalink automatically. This then moves a few sections from the manual to their own pages in Docs:

  • 1 Overview
  • 5 Building Applications
  • 6 Importing Applications
  • 7 Metadata
  • 8 Update Processing
  • 10 Signing

Other sections of the manual overlap with material from the wiki, so they need to be merged and edited heavily. Those are coming in a separate MR.

This also removes the Google tracking via its fonts API by including the free open source Roboto font in this repo.