Also:
* Clear the newtalk flag when they mark all their edit-user-talk
read.
* Remove the section caching system. It was designed to avoid
performance problems with Flow messages, but now that standard talk pages
are in 'messages', messages should be relatively common (alerts
were already not cached by this).
* Minor cleanups to reflect that messages are not only Flow (and
a typo fix in the Gruntfile).
Bug: T108760
Change-Id: I82d7b1d08331693830d6a1749612b55e96b95cf9