Support for SALTED index.

CREATE INDEX supports a new clause "SALT LIKE TABLE".
This causes SALT column to be leading column in the index
Duplicate columns in the index table are now eliminated. This is a bugfix.
Showddl and Invoke will show the SALT syntax and column respectively for
the index. CREATE index also supports HBASE_OPTIONS clause.
A bug seen when NULLABLE partitioning columns are used is also fixed.

Patch Set 2 : All rework from Patch Set 1, excpt for NATable.cpp

Patch Set 3 : Rework in NATable.cpp. Thanks to Hans for all help. Nullable
partition key columns will now generate evenly distributed dataflow through
esps.

Patch Set 4: Fix 3 issues found for the work done in Patch Set 3. Change is only in NATable.cpp

Change-Id: If378ffca29ee83dd4b7928c784b8d34d76f50049
Merge "Support for SALTED index."