[FIXED JENKINS-19898] test base classes should not be linked to the junit implementation.

Changed the return type to be generic and not the junit specific CaseResult.

TestObject.fullName was used in the baseClasses jelly but this was only defined in the CaseResult so add an implementation to the base class such that people can continue to use the generic jelly in their cusomt test implementations.

Change-Id: I39fbff6621d7f20f9cebb210eea4f54a90f77375
Merge pull request #998 from jenkinsci/jenkins-19898

[FIXED JENKINS-19898] test base classes should not be linked to the junit implementation.