Generation of rudimentary distributed plans for analytic exprs.

Change-Id: I14038a34371ccf74a1e2d174203f7a5898a31819
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4034
Reviewed-by: Marcel Kornacker <marcel@cloudera.com>
Tested-by: jenkins
Adding VARCHAR front & backend.

VARCHAR is treated as StringVal in the backend. All UDAs and UDFs which accept STRING
will also accept VARCHAR(N).

TODO: Reverted Avro codegen to fix Jenkins; needs separate patch.

Change-Id: Ia90d7d6d3ed590dbe2cfd981139c24e512dc5df2
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/2527
Reviewed-by: Victor Bittorf <victor.bittorf@cloudera.com>
Tested-by: jenkins