XLS checklist crash / New format checklist tracking issue

@GoForPDI noted in the Spaceflight Server #nassp channel that LibreOffice was not supporting XLS checklists properly and causing a crash. It's probably a good idea to have an issue here to track if, or when, NASSP will switch over to using something other than XLS for checklists as it is my understanding that this has been talked about before. Obviously, it's not quite the best that only proprietary software can be used to properly and conveniently edit this open source project's data files.

I'm willing to implement such a change and convert the checklists, but it will probably not be until I finish my Orbiter SDL3 port, which may be a while so anyone else is open to implement this as well, obviously.

The particular format is an important choice; I think making a parser for a simple definition language, or using a standardized text format such as JSON (or probably something better than JSON) would be helpful rather than trying to shove CSV/TSV into this and hoping it works; also, CSV/TSV can be kind of irritating to deal with, as they're not well specified and have some pain points around using the delimiter character (i.e., quotes for , or tabs for CSV/TSV respectively)

For the time being, until such a large change is implemented, it is likely worth debugging the LibreOffice-made sheets and seeing what causes it to crash the Checklist MFD.