[FEATURE] Specify attribute type

[ahalota]

By default, dbf library is taking any number attributes and turning them into 3 decimal point floats.
For things like an id or count column, this doesn't make sense.
Would be useful to add an option for the user to specify the type they want associated with certain columns (in case you have one that happens to be all ints, and you also want to define it as int only)