Convert to storing current fields in JS vs on the form

Once we do that, revert the date format here and always use a normal YYYY-MM-dd date: https://github.com/programcsharp/griddly/commit/cfa322c114a0fc56c050ce00aa495fab6b1ab8d0#diff-416edfdc6b0c874e392672e1a682549aL158

Don't include time cuz we don't need that shenanigans here.