DATAREDIS-305 - Add support for HSCAN.

HSCAN is directly supported by jedis and can be emulated for lettuce via eval.

SRP and JRedis will throw UnsupportedOperationException.

We have modified the ScanCursor implementation to take Collection instead of List.

Currently naming for scan commands is not consistent for scan, sscan and hscan. There’s a clean up task for those commands when done with all scan related commands.

Original pull request: #78.