Adds join projection, comments for join classes, removes unsupported methods for join.
Added unit test for join projection
Extended Join integration test for join projection
All sink methods in DataSet return the DataSink object to allow setting parameters.
Improved error message in PackagedProgram for preview plans.
Fixed pre-packaged end-to-end test.
Add projection cross
Minor fixes in JavaDocs and parameter checks
Unit tests to check for valid parameters of cogroup
Activated unit test for CoGroupOperator
Default cross operator
Combinable GroupReduce for new Java API
Changed key handling for key-selector combiners
Move testing utils and data to package stratosphere-test-utils

When trying to use packages that use stratosphere-tests in
stratosphere-examples you used to get a circular dependency. Now
packages can use the testing utilities without pulling in all the
transitive dependencies of stratosphere-tests.
Remove bin/ directory from tests and test-utils
Remove old TestBase, rename TestBase2 -> RecordAPITestBase