Fix searching/filtering bugs #235

- Fix a bug (introduced in 1b9be8fe) preventing the tree view from being
  visible during a search.
- Fix a minor bug where the scripts view does not render based on the
  initial filter.
- Add Vue component tests for `TheScriptView` to prevent regressions.
- Refactor `isSearching` in `TheScriptView` to simplify its logic.

src/infrastructure/Events/EventSubscriptionCollection.ts

@@ -1,6 +1,7 @@
 import { IEventSubscription } from './IEventSource';
+import { IEventSubscriptionCollection } from './IEventSubscriptionCollection';
 
-export class EventSubscriptionCollection {
+export class EventSubscriptionCollection implements IEventSubscriptionCollection {
   private readonly subscriptions = new Array<IEventSubscription>();
 
   public register(...subscriptions: IEventSubscription[]) {