Improve error messaging for malformed simfiles

[bkirz]

A user uploaded a chart to the mine faker with an orphaned hold head, which raised an OrphanedNoteException and gave them an unhelpful 500 page. We can't and shouldn't attempt to handle all malformed inputs, but our error messaging could be clearer. Maybe we allowlist a set of known error-types and come up with a better error message if one of those is caught?