Feature: Add CSV import functionality

[JannikStreek]

Further Notes

Currently, our export is very basic and doesn't reflect the lane changes. If the export is updated to the current version, we can also offer import functionality, meaning parsing a CSV file and adding ideas and columns automatically as a template. That would be interesting to restore a default template for users.

[PragTob]

I wonder how that'd be laid out in a CSV as the data is fairly complex - multiple lanes, labels, ideas in them with comments even.

Unless users need CSV I think I'd advocate for a JSON export/import.

Since the formats will change, the question is also how many "older" formats should be supported.

It's probably not applicable here as it can't work across deploys but there is also erlang.term_to_binary and the binary format: https://www.erlang.org/doc/apps/erts/erl_ext_dist.html (would/should work against the same code version/same deploy - but would also include id and other data so not a stripped down versiont aht one would likely want)