1. Add include/utilities/write_batch_with_index.h, providing a utility class to query data out of WriteBatch when building it.
2. new ReadOptions.total_order_seek to force total order seek when block-based table is built with hash index.
**Public API changes**
1. The Prefix Extractor used with V2 compaction filters is now passed user key to SliceTransform::Transform instead of unparsed RocksDB key.
2. Move BlockBasedTable related options to BlockBasedTableOptions from Options. Change corresponding JNI interface. Options affected include: no_block_cache, block_cache, block_cache_compressed, block_size, block_size_deviation, block_restart_interval, filter_policy, whole_key_filtering. filter_policy is changed to shared_ptr from a raw pointer.
3. Remove deprecated options: disable_seek_compaction and db_stats_log_interval
4. OptimizeForPointLookup() takes one parameter for block cache size. It now builds hash index, bloom filter, and block cache.
