* Move CSS definitions to resources
* Add Gtk::Builder helpers
* Switch StatsDialog to Gtk::Builder
* Switch RelocateDialog to Gtk::Builder
* Switch OptionsDialog to Gtk::Builder
* Switch MakeDialog to Gtk::Builder
* Switch FilterBar to Gtk::Builder
* Switch MainWindow to Gtk::Builder
* Switch MessageLogWindow to Gtk::Builder
* Switch DetailsDialog to Gtk::Builder
* Switch PrefsDialog to Gtk::Builder
* Fixup translatable strings
Since this branch was brewing for a while, changes happened in the meantime.
There is a fallback mechanism in GTK: when looking for an icon named
foo-a-b-c, it'll also try to find foo-a-b, foo-a, and foo, so the only
icon necessary (if all of them default to the same one) is foo. Given
that we're also installing this icon, including it in resources doesn't
make a lot of sense, by I'm leaving it just in case anyway (useful when
debugging without installing).