Fully disable all mwlib formats; use OCG service instead.

The mwlib server is to be deactivated October 6.  Purge all mention of it
from the configuration files.  Enable experimental OCG plain text backend
on beta.

Change-Id: Iece8304f69bf6b6c7699569a1384b7ba0035f52e
Merge "Fully disable all mwlib formats; use OCG service instead."