Be upfront about Special:PageTranslationDeletePage permissions

Check permissions as first thing to avoid wasting the user's time:
first 'pagetranslation', because most visitors are sysops coming
from action=delete button so they have 'delete'.

<https://www.mediawiki.org/wiki/Thread:Help_talk:Extension:Translate/Required_rights_for_%22Special:PageTranslationDeletePage%22>

Change-Id: I3e734ba1ad6dc7414a555c31f0e4cb26426102ec
Merge "Be upfront about Special:PageTranslationDeletePage permissions"