Minor fixes (i18n and special page group)

This fixes the description of 'right-centralauth-lock' (that
right changed in I745d252056795fa3631e40f65f9aeef519c94fdb),
the action text for centralauth-lock, the Qqq for action-
centralauth-lock and sets the special page group 'users' for
the new MultiLock.

Change-Id: I8a20cdce1bcf6d95364f6323b6248070314b5256