Breakdown CSS: split out the resource browser

Now that everything has been converted to scss, splitting out the
individual components of our CSS can and should begin!

In an effort to do small changes (to keep them mergable and reviewable)
I'm only splitting out the resource browser stuff.  I'm trying to
balance the style that Maxime has used throughout the previous reviews
relating to this blueprint while also not changing everything that can
be changed.

Change-Id: Ibc9fb11163883498384e963210067e9600fbca9d
Partially-Implements: blueprint css-breakdown
Merge "Breakdown CSS: split out the resource browser"