docs(app): fix styling of left sidenav, add FontAwesome

Since the structure was a little different than the prototype,
classes/styles where not applied correctly to the links in the left
sidenav. This commit fixes the issue.

I also added FontAwesome, in order to be able to display icons until the
Material Design icon-font is released. Since this is a temporary meassure,
I didn't added as a bower dependency; just added a `font-awesome` folder
in assets and added `font-awesome/css/font-awesome.css` to the stylesheets
of each deployment (under `docs/config/services/deployments/`.