Allow PerformanceRunner to run tests provided by a factory method

1. I have modified PerformanceRunner to be able to run tests provided through a factory method annotated with @PerformanceTestFactory, when used with @PerformanceTestSuites. The method can be used (this is optional) on a "test case" object that is added to the ParameterizedTestList returned by the @PerformanceTestSuite method. If there is no @PerformanceTestFactory method, the behaviour stays the same as before. If a @PerformanceTestFactory exists, the PerformanceRunner adds all the test case instances returned by the factory to the testObjects list, instead of the test case itself.
Optionally, the test cases can implement an IdentifiableTestCase interface, which gives the ability to have custom names for tests running on different instances.

The motivation behind this is that a suite can contain test cases that are different logically, but the test case should be able to be parameterized.