[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/context-menu/context-menu.component.spec.ts

@@ -111,7 +111,9 @@ describe('ContextMenuComponent', () => {
       .querySelectorAll('button');
 
     expect(contextMenuElements.length).toBe(1);
-    expect(contextMenuElements[0].innerText).toBe(contextItem.title);
+    expect(contextMenuElements[0].querySelector('span').innerText).toBe(
+      contextItem.title
+    );
   }));
 
   it('should run action with provided action id', fakeAsync(() => {