Feature: Lazy loading

Lazy loaded everything
TODO: The cash flow module when clicking on sub-links, it reloads the whole page, it needs to be diagnosed and fixed, this problem also exists in the other modules
TODO: Rename folders and modules such as account to accounts to match the url

overlord/src/app/core/cost-centre.ts

@@ -0,0 +1,5 @@
+export class CostCentre {
+  id: string;
+  name: string;
+  isFixture: boolean;
+}