Fix JDK import in the inheritance study

[DavidRFerreira]

Context:
Dietrich added the source of OpenJDK in the _contractstudy/lib/openjdk/ directory_. This was done to capture more supertype relationships resolved against the Java core class libraries.

Issue:
Download and add OpenJDK to the correct path.

The ComputeInheritanceHierarchy script tries to load the OpenJDK source code to identify its methods and inheritance relationships.

But when this is done, the application gets the error java.lang.OutOfMemoryError: Java heap space: failed reallocation of scalar replaced objects

Expected Behaviour:

Fix the issue so that we are able to load the OpenJDK to get more significant results in the inheritance study.