Change the representation of DataType.INTEGER values from `java.lang.Integer` to `java.lang.Long`

[vruusmann]

This is a major (although non-breaking) change, so it should be scheduled to happen in the beginning of the 1.5.X development series.

[XciD]

I can contribute to this feature.
I've tested it, it's working like a charm on our side.

[vruusmann]

I'm more interested in the explanation of why is the switch from Integer to Long needed?

[XciD]

We have some backend that generate timestamp in nanoseconds....