Remove font-related styles from default (non-Vector) CSS:

* This includes all font-family, most font-size, and all explicit line heights.
* Also, change to use relative paths.
* Remove duplicate font-size.

Patch Set 8 removes the static test/{monobook,vector}/login files
demonstrating the change that were in earlier patches.

Change-Id: Ie3b30962dee36b43cdb70bd6c9d897317378b861