Use ng2-pdf-viewer

And remove now-unused safeUrl pipe

src-ui/src/app/pipes/safe.pipe.spec.ts

@@ -1,8 +0,0 @@
-import { SafePipe } from './safe.pipe';
-
-describe('SafePipe', () => {
-  it('create an instance', () => {
-    const pipe = new SafePipe();
-    expect(pipe).toBeTruthy();
-  });
-});