this commit does some general tidyup of how we handle some
of the CSS and font files.

First, the two fonts we use, open sans and fontawesome are now
set up to be pulled down from the central copies we have hosted
on apps.fp.org/global. Note that due to CORS restrictions, this
means these fonts will work on prod, but not when testing locally.
If you install the fonts locally on the system you are looking at
the test site at, it will use the fonts. Details on this have been
added to the dev documentation.

Second, we remove the cantarell and comfortaa fonts in the repo,
as these were not being used. We also delete the style-patternlab.css
file that was not being used either.