Support RocksDB key-value store

[vijay03]

Enable RocksDB to run on top of SplitFS

[vijay03]

@OmSaran do you want to take a shot at this?

[OmSaran]

@vijay03 Yup, I'll give this a shot!

[OmSaran]

#31 includes changes to support rocksdb examples and rocksdb on YCSB.