Merge branch 'update-to-angular-12' of https://github.com/iqb-berlin/testcenter-frontend into update-to-angular-12

Prepend UTF-8 BOM to csv raw data #162

Fix block-selection in group-monitor: It only registered the click, when the text was clicked, not the whole element.

Fixes https://github.com/iqb-berlin/testcenter-frontend/issues/312

While applying the new linting-rule no-param-reassign, I made a mistake and corrupted the function getNextUnlockedUnitSequerceId (commit #e88e136d). This broke the navigation in some circumstances.

Fixes #https://github.com/iqb-berlin/testcenter-frontend/issues/304

(For some reason) the workspace id is not set yet when entering 
files.component.ts, so by delaying (setTimeout), the workspace id has 
the correct value. Then, the url for file upload is set correctly.

This reverts commit 7288c888.

closes #299

Remove @SkipSelf in TestControllers's Services, because it works only without (for what reason ever).

That was necessary because the dependency injection was changed in teh new angular version. The encapsulated upload-module got it's own instance of http client und thus the interceptor did not kick in (even when http was injected with @SkipSelf).

Tidy up the upload component, add types etc.

Does not work properly yet.

Otherwise the auth/error-handling-interceptor will not kick in.

See: https://dev.to/angular/that-s-why-your-angular-errorinterceptor-may-not-work-5-seconds-fix-52m8

This have to be added be added to other modules as well I guess.

-> compiles but does not work properly

Compodoc is a documentation tool for Angular applications
which generates static html documentation pages.
A documentation of Testcenter Frontend can be build with
```
npm run compodoc
```
I can be viewed under http://127.0.0.1:8080