DATAFU-70: added generic BagJoin that supports inner, left, and full outer joins

https://issues.apache.org/jira/browse/DATAFU-70

Signed-off-by: Matthew Hayes <matthew.terence.hayes@gmail.com>
Update BagJoin for JRE 1.6 compatibility
Minor improvements to BagJoin constructors, add an inner join test for BagJoin
DATAFU-77 Fix test.sh to use gradlew.

https://issues.apache.org/jira/browse/DATAFU-77

Signed-off-by: Matt Hayes <mhayes@linkedin.com>