Fix DiskManager JSONObject import.
Add org.json dependency from metastore.
Add PartitionIndex and PartitionIndexStore table and related JDO classes.
Merge remote-tracking branch 'origin/zjw' into test
Merge from zjw's branch for partition related rpc fixing.
Implement add/drop_subpartition_files.
Merge from branch zjw:bf5c84
Merge remote-tracking branch 'origin/zjw' into test for the first alpha release.
Fix show ddl bugs