Add a MemoryTableDesc wrapper around a table RDD, or partition RDDs if the table is Hive-partitioned.
Comment in SharkSemanticAnalyzer about handling CREATE TABLE and CTAS.
Move CREATE TABLE/CTAS analysis to a new method.

This includes adding a new QueryBlock that's used to store detected cache modes.

Also, renamed MemoryTableDesc to MemoryTable.
Return union of all Hive-partition RDDs for SharkEnv#unpersist() and MemoryMetadataManager#unpersist().

Also added Option[RDD[_]] in MemoryTable to represent an empty table.
Header comment for QueryBlock.
Disable cached, Hive-partitioned tables for now.
Update some comments in MemoryTable, fix small SharkSemanticAnalyzer compile bug…
Add an isHivePartitioned() fn to MemoryMetadataManager.

Helpful for testing.
Add TODO for creation of cached tables using non-CTAS CREATE TABLE.
Fix comment about QBs in SharkSemanticAnalyzer.
Better variable name for QueryBlock's cache mode.
Don't error out in put() and putHivePartition() for now.
Table names added in MemoryMetadatamanager should be case-insensitive....
More comments and minor refactoring of SharkSemanticAnalyzer.
Merge remote-tracking branch 'ampshark/master' into partition-caching
Revise some added comments.
Merge remote-tracking branch 'ampshark/master' into partition-caching