Very many testcases, some GLib tools (resource compiler, etc) and
GApplication were calling g_type_init().
Remove those uses, as they are no longer required.
https://bugzilla.gnome.org/show_bug.cgi?id=686161
This tests the interaction between mimeinfo.cache, defaults.list and
mimeapps.list to ensure g_app_info_set_as_last_used_for_type doesn't
incorrectly change the default.
https://bugzilla.gnome.org/show_bug.cgi?id=658188