Enable Translate extension on OTRS wiki

This patch enables the Translate extension on the OTRS
wiki per request from OTRS administrators.

In line with the default settings, bureaucrats will be
able to add and remove users from the 'translationadmin'
group. Since OTRS wiki does not require many translation
states, we'll be using Niklas's suggestion from bug 41585
comment 3, including automatic state changes.

Following another advice from Niklas, translation memory
will be disabled as OTRS wiki is private.

To make things easier on OTRS wiki bureaucrats, local
sysops will be able to add and remove themselves from the
'translationadmin' user group.

Bug: 61297
Change-Id: I845f07a9403e8bfdcc525efbc4badf82c7ea0409