does not work yet, we always get back a 400 when
logo or image are not null in json format

have to find out how the exact format and encoding has to be to update
a show inlcuding files

When we use the image and logo values in the show object directly,
we get errors, when those values are 0, because they are rendered,
just not visible.

So we use intermediate values now in the this.current object, which
are set everytime the show is switched.

HTML rendering did not work anymore as before - probably due to changes in bootstrap-vue?
So now adapted and in the same time improved rendering.
Now with images for edit buttons.
And if no title is set, this is mentioned now.

Relevant bootstrap-vue docs:
* https://bootstrap-vue.js.org/docs/components/table#custom-data-rendering

New following a different approach to static assets.

See https://www.jerriepelser.com/blog/using-auth0-with-vue-oidc-client-js/
for how to use OIDC client with the npm sources and per-compile updating
the static asset.

Also environment variables now work a bit differently.

Updated README.md accordingly

Superusers should see all shows. Ordinary users only those shows that belong to them.
Therefore we have to fetch the user data from the steering backend as well (OIDC info
alone does suffice here).

We need this info later too, when we implement user managament and profile settings.

In the ShowManager we now generate the GET URI depending on the superuser status.

still TODO regarding OIDC:
* handle token expiration and refreshing

still TODO regarding ShowManager:
* finalize all requests for ShowManagerModal*
* change getting notes: we now have a note_id in every timeslot
* handle repetitions when updateing timeslots & notes
* creation of new timeslots and collision handling

includes:
* new pretty date functions
* fetching of timeslots through getTimeslots function

now prepared for pagination, has to be implemented next

includes:
* new pretty date functions
* fetching of timeslots through getTimeslots function

now prepared for pagination, has to be implemented next