[ACA-2064] support custom icons for extensions (#864)

* icon component, custom svg

* split components, fix modules

* simplify code

* universal icon component

* support custom icon registration

* update docs

* test fixes

src/app/components/layout/app-layout/app-layout.component.ts

@@ -44,8 +44,6 @@ import { currentFolder } from '../../../store/selectors/app.selectors';
 import { AppStore } from '../../../store/states';
 import { BreakpointObserver } from '@angular/cdk/layout';
 import { SetSelectedNodesAction } from '../../../store/actions';
-import { MatIconRegistry } from '@angular/material';
-import { DomSanitizer } from '@angular/platform-browser';
 
 @Component({
   selector: 'app-layout',
@@ -70,25 +68,14 @@ export class AppLayoutComponent implements OnInit, OnDestroy {
   private minimizeConditions: string[] = ['search'];
   private hideConditions: string[] = ['preview'];
 
-  customIcon: any = {
-    join_library: './assets/images/join-library.svg'
-  };
-
   constructor(
     protected store: Store<AppStore>,
     private permission: NodePermissionService,
     private router: Router,
     private userPreferenceService: UserPreferencesService,
     private appConfigService: AppConfigService,
-    private breakpointObserver: BreakpointObserver,
-    matIconRegistry: MatIconRegistry,
-    sanitizer: DomSanitizer
-  ) {
-    matIconRegistry.addSvgIcon(
-      'join_library',
-      sanitizer.bypassSecurityTrustResourceUrl(this.customIcon['join_library'])
-    );
-  }
+    private breakpointObserver: BreakpointObserver
+  ) {}
 
   ngOnInit() {
     this.isSmallScreen$ = this.breakpointObserver