Detect signature using Title class

Currently echo attempts to find a signature by looking for a series of
strings starting with what it thinks are the current aliases of NS_USER
and NS_USER_TALK.  This has shown to be error prone, see the linked bug
for how a change to ru.wikipedia.org/wiki/Mediawiki:Signature broke
mention notifications.

Patch switches things arround to pull wikilinks out of the text and run
them through the Title class.  The results of this parsing are checked
for NS_USER and NS_USER_TALK, giving a much stronger guarantee of finding
translated namespaces.

Bug: 71353
Change-Id: Ib0d0f4e068339d2fd28761087c05f5a1acb3c1fc
Merge "Detect signature using Title class"