TAJO-1952: Implement PartitionFileFragment
See https://issues.apache.org/jira/browse/TAJO-1952 and https://github.com/apache/tajo/pull/846. I recreated a pull request because of a branch deletion mistake.
Not ready to review. After recent rebase, some unit tests fail. I'm trying to fix it.
At first, I approached to make another fragment for partitioned table. But now, the only difference between FileFragment and PartitionFileFragment is the partition key. So, I would prefer to add the variable to FileFragment instead of making PartitionFileFragment. It will decrease unnecessary modifications and will avoid side effects by PartitionFileFragment. Here are codes by above approach. https://github.com/apache/tajo/compare/master...blrunner:TAJO-1952-2?expand=1.