Show different title when Special:CentralAuth shown in read-only mode

When [[Special:CentralAuth]] page shown up as read-only mode, display
"Global account info" instead of "Global account manager" for page
title. And this patchset change legend's header also.

Bug: 27142
Change-Id: I8bd030d464d708a85a622dbde9b8a403e8c8fd6c