[SPARK-2523] [SQL] [WIP] Hadoop table scan bug fixing

In HiveTableScan.scala, ObjectInspector was created for all of the partition based records, which probably causes ClassCastException if the object inspector is not identical among table & partitions.

This is the follow up with:
https://github.com/apache/spark/pull/1408
https://github.com/apache/spark/pull/1390
I should make a better document, actually `Row` is the sub interface of `Seq`.