If the translations are stripped off into gettext .mo files, as happens
on Ubuntu, we need to be operating in the right locale so that
g_desktop_app_info_get_description (et al.) read them out correctly.
Previously we were doing work in init(), which is after gtk_init() calls
setlocale().
Move the population of the model to startup(), and chain up first, so
that it happens after we're fully initialised (including the locale).
https://bugzilla.gnome.org/show_bug.cgi?id=791035
Replace the gnome-shell builtin settings search, which relied on removed
menu files, with one that uses the remote search infrastructure and
CcSearchModel, and features the ability to continue searching within the
control center application.
https://bugzilla.gnome.org/show_bug.cgi?id=690577
