Implement ClientSchedule state tracking class

Write the logic of keeping track of location modifications and applying
updates from the server into the ClientSchedule class.  This should
serve as the foundation for replacing the prototype in-component update
logic which have turned into an unmaintainable spagetti.

shared/utils/luxon.ts

@@ -0,0 +1,11 @@
+// Wrapper around Luxon to make sure the throwOnInvalid option is set
+import { Settings, DateTime, FixedOffsetZone, Zone } from "luxon";
+
+Settings.throwOnInvalid = true;
+declare module 'luxon' {
+	interface TSSettings {
+		throwOnInvalid: true;
+	}
+}
+
+export { DateTime, FixedOffsetZone, Zone }