trivial: Make compression optional in as_store_to_file()
trivial: Make compression optional in as_store_to_file()

ikeydoherty/appstream-glib,hughsie/appstream-glib,superm1/appstream-glib,ikeydoherty/appstream-glib,ximion/appstream-glib,kalev/appstream-glib,hughsie/appstream-glib,superm1/appstream-glib,mitya57/appstream-glib,ximion/appstream-glib,hughsie/appstream-glib,mitya57/appstream-glib,kalev/appstream-glib,ximion/appstream-glib