Fix bug that incorrectly marked iterative tasks.
Added standalone plan visualizer tool.
Add LineRank as test case.
Add Scala Page Rank examples
Fixed ExecutionGraphTest. Test output files are removed. Reduced log level to WARN.
Add constructors with degree of parallelism argument to Plan (issue #426)
Improve error message when no match is found in solution set join (issue #429)
Add check whether group is empty in scala reduce operator

This fixes #434
Reenable ClosureCleaner and add new Test case for everything

Closure cleaner did not work before because the user code class loader
was not used when it was trying to load inner anonymous classes.

The new test checks whether the ClosureCleaner works together with the
user code class loader.

It also used the local distributed executor and remote executor.