Feature/progress widget (#760)

* Implemented a new widget to show when operations are occuring in the backend (tasks + progress events). Fixed an oversight on progress reporting where I sent 100F instead of 1F.

* Hooked in more progress events for tasks on the backend. Cleaned up code and integrated some RBS into it. CSS needed.

* Show a colored icon when events are active

* Added some styling to the progress widget

UI/Web/src/app/_models/events/scan-library-progress-event.ts

@@ -1,4 +1,4 @@
-export interface ScanLibraryProgressEvent {
+export interface ProgressEvent {
     libraryId: number;
     progress: number;
     eventTime: string;