Support range partitioning

Due to specific customer demands, we need the ability to partition using pre-defined ranges of values. For us, it is `long` values, but I suppose for others it could alphabetical, or whatever. A couple of issues immediately come to mind with this problem:
1. AFAIK, the addition of more shards after the initial process is not supported. This would likely need to change as pre-determining all the ranges would be impractical in many scenarios.
2. One could imagine a scenario where multiple ranges might want to map to the same shard. I _think_ this is supported in the table metadata structure, but if not, then this could be an issue, too.