Changed absolute url refs in css files to relative urls.

/static/cms/ should not be hardcoded in the css files.
Revert "Changed absolute url refs in css files to relative urls."

This reverts commit 8b74d65ed0af8469914385e7fffd2bfdfa21377d.
Revert "Revert "Changed absolute url refs in css files to relative urls.""

This reverts commit c0e1141c552cf96760b21b447403a97c518644ed.