Allow Force-Delete of Formats in UI

Currently, when a format is still in use, the backend forbids the user from deleting it. It would be good to have an option to delete it anyway, or at least provide a list of meetings where it is used.

For instance, after Covid, a lot of meeting had covid related formats that were no longer relevant. We had to find the individual meetings that were using each, change the meeting and then delete the format.

After #1401 is complete, we can just use the DB delete cascade to do this for us. Obviously, only after special confirmation from the user.

Alternative might be to add a lookup by format to the meeting search....