Update ScoreboardMergeCommand

[RagnarGrootKoerkamp]

Some changes I made:

1. Allow reading from local files directly. It turns out to be more reliable to first download scoreboards from the API and then merge them when servers go down after the contest. (This needs e.g. - /path/to/scoreboards:/scoreboards in the docker-compose.yml which needs to be added manually.)
2. Do not check that group IDs look like integers -- they can be strings.
3. Match problems by display name instead of ID, since sites differ in whether they use A or problemshortname as ID.

I also had to disable showing the banner image, but I changed that by commenting it out in the twig. This needs some better fix.

(More comments in the script in BAPCtools that uses this.)

[nickygerritsen]

Can you look into the annotations reported by phpstan and the codestyle? Afterwards we can merge I tihnk.

[RagnarGrootKoerkamp]

All should be/become green now

[nickygerritsen]

Thanks!