Adding support for {anti,left semi,left outer} joins to the partitioned hash join implementation.

Adding the "anti join" keyword in the frontend and the corresponding backend paths for the
partitioned hash join implementation.  Adding some basic testing for this new join (the
other types have already tests).

Also, fixing a bug in the tuple stream when it was handling strings.

Change-Id: Ied8cff96b2bca284a5f66f7d11df5c5b5ec789cc
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/3805
Reviewed-by: Ippokratis Pandis <ipandis@cloudera.com>
Tested-by: jenkins