Settings : Add title to xml preference screens

Search indexing was inserting null as the title, which results
in the default "Settings" title if the user selects a search result.
This is inconsistent with the title the user sees when they manually navigate
to that preference screen.

FEIJ-512

Change-Id: I6f6ed7b851c998aa2cb5531bef04e8000ccb8ddd
(cherry picked from commit 9dc803c7)