Prepared query does not allow to specify datacenter

[teoincontatto]

Hello,

First of all thanks for this nice library to wrap Consul REST API in a confortable Java API.

I found that in the prepared query API it is not possible to specify the datacenter (field "dc" in Consul REST API). I know it is not so common use case but I think it would improve the project quality to have it.

Cheers,
Matteo