[Java] Add Java bindings for memtables and sst format.

Summary:
Add Java bindings for memtables and sst format.  Specifically,
add two abstract Java classses --- MemTableConfig and SstFormatConfig.
Each MemTable / SST implementation should has its own config class
extends MemTableConfig / SstFormatConfig respectively and pass it
to Options via setMemTableConfig / setSstConfig.

Test Plan:
make rocksdbjava
make jdb_test
make jdb_bench
java/jdb_bench.sh \
  --benchmarks=fillseq,readrandom,readwhilewriting \
  --memtablerep=hash_skiplist \
  --use_plain_table=1 \
  --key_size=20 \
  --prefix_size=12 \
  --value_size=100 \
  --cache_size=17179869184 \
  --disable_wal=0 \
  --sync=0 \

Reviewers: haobo, ankgup87, sdong

Reviewed By: haobo

CC: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D17997

java/org/rocksdb/TableFormatConfig.java

@@ -0,0 +1,20 @@
+// Copyright (c) 2014, Facebook, Inc.  All rights reserved.
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+package org.rocksdb;
+
+/**
+ * TableFormatConfig is used to config the internal Table format of a RocksDB.
+ * To make a RocksDB to use a specific Table format, its associated
+ * TableFormatConfig should be properly set and passed into Options via
+ * Options.setTableFormatConfig() and open the db using that Options.
+ */
+public abstract class TableFormatConfig {
+  /**
+   * This function should only be called by Options.setTableFormatConfig(),
+   * which will create a c++ shared-pointer to the c++ TableFactory
+   * that associated with the Java TableFormatConfig.
+   */
+  abstract protected long newTableFactoryHandle();
+}