New default setting

Added $wgRestrictDisplayTitle to our DefaultSettings.php

This is because otherwise only "capitalization variations" are allowed,
which is good and recommended in public community wikis but contra
intuitive in business wikis.

[1] https://www.mediawiki.org/wiki/Manual:$wgRestrictDisplayTitle

Change-Id: I15add5529f770ddf855afc285ac7c57b48aedb8f
Merge "New default setting"