Summary:
* Add java api for rocksdb::WriteBatch and rocksdb::WriteOptions, which are necessary components
for running benchmark.
* Add java test for org.rocksdb.WriteBatch and org.rocksdb.WriteOptions.
* Add remove() to org.rocksdb.RocksDB, and add put() and remove() to RocksDB which take
org.rocksdb.WriteOptions.
Test Plan: make jtest
Reviewers: haobo, sdong, dhruba
Reviewed By: sdong
CC: leveldb
Differential Revision: https://reviews.facebook.net/D17373
