GIRAPH-708: Factories for creation of all IVEM types (nitay)
Merge remote-tracking branch 'origin/trunk' into jython-scripts

Conflicts:
	giraph-core/src/main/java/org/apache/giraph/graph/GraphTaskManager.java
	giraph-core/src/main/java/org/apache/giraph/jython/JythonComputationFactory.java