Added a function getRightsWarningMessage() to Utils

The function returns a string with the appropriate rights warning
message. Duplicate code from EntityView.php was replaced with a function
call. Function calls also added to SpecialNewEntity.php and SpecialSetEntity.php

Bug: 45773
Change-Id: I1a5981f56fff9c7b198fda4579670345f4734794
Merge "Added a function getRightsWarningMessage() to Utils"