Summary:
Adding SSTFileWriter's newly introduced put, merge and delete apis to the Java api. The C++ APIs were first introduced in #2361.
Add is deprecated in favor of Put.
Merge is especially needed to support streaming for Cassandra-on-RocksDB work in https://issues.apache.org/jira/browse/CASSANDRA-13476.
Closes https://github.com/facebook/rocksdb/pull/2392
Differential Revision: D5165091
Pulled By: sagar0
fbshipit-source-id: 6f0ad396a7cbd2e27ca63e702584784dd72acaab