Added support for local distributed execution environments.

Conflicts:
	stratosphere-tests/src/main/java/eu/stratosphere/test/util/AbstractTestBase.java
Fixed free memory calculation bug in case where multiple task manager run on the same jvm.
Removed local distributed executor environment from user api. Now only used for testing
Added setter and getter for numTaskManager in NepheleMiniCluster. Updated WordCountITCase and PackagedProgramEndToEndITCase accordingly.