OpenJPA compatibility

Patches to make human-task-services work with OpenJPA. 

All tests still pass when using Hibernate. Most tests pass when using OpenJPA but there seams to be a problem with Weld and OpenJPA which I could not fix. I will look into that later.

There are two maven profiles: hibernate and openjpa. hibernate is default.

Run mvn clean test -P openjpa to execute the tests using OpenJPA
Hello Friend,
                    We can remove this conditional statement, since pareseBoolean() method accept 'null' too as parameter. Reference - https://docs.oracle.com/javase/7/docs/api/java/lang/Boolean.html#parseBoolean(java.lang.String)

Cheers!!!

Sambath Kumar Logakrishnan