Lazy CSV field selection

[ShadenSmith]

Right now the field selection of CSVs is case insensitive. It would be nice to to only only require the minimum unique starting characters (e.g., "date of transaction" -> "date").

[ShadenSmith]

In the event of an incomplete field name being specified, the .map file that is generated should be the full field name, all lowercase. We should probably already standardize that.