NuCivic/dkan#298 Select the right data table column type

Thought about this. If your regex checks for integers, then for floats, then for datetimes and then for bigtexts, the resulting type should be the most comprehensive. So integer only if all values are integer, float only if all values are either float or integer, etc. I'm not so sure about datetime though.

I tested this with integers and floats.