* ui: Convert Service.GatewayConfig to a model fragment
We added the ember-intl addon, which has its own format-number helper.
We replaced our own similarly named helper with this one, but the
ember-intl one is far stricter and errors if the arguments passed are
undefined. Our previously one would cope with this.
We'd rather continue to use the stricter ember-intl helper, so here we
convert the GatewayConfig property to a model fragment so that we can
give the GatewayConfig.AssociatedServices property a default zero value.
