Move Vector's preferences css out of screen.less

* Move the preferences styling out of screen.less,
  no need to penalise all our users with it.
* Limited to Vector skin for time being as other skins do not play nicely
  with these styles.

Change-Id: I121b3d88945d994c9e30d96bab7548c839510276
Merge "Move Vector's preferences css out of screen.less"