Would like also to add mimetype to the list. I would prefer not to have a key at all it this case

[file_extension, english_description, mimetype, [alternate_input_value1, ...]]

Alternate as would also accept first 3 as possible value as well.

csv would be good but do not really like variable length ones.  Would happier with semicolon seperated (or tab seperate)  as would want to put some json in field and commas are a painful todo that with due to escaping.  

```
file_extension description; mimetype; alternate_input_values
CSV; CSV File; text/csv; ["wierd csv input 1"]
```