Make testRunnerAdapter.test(...) more flexible

On client side a test case in a test class is represented by java.lang.reflect.Method. This makes impossible to easily integrate frameworks like ScalaTest, where a test case is not necessarily a class method.

As a solution, it would be great to:

(a) relax the test representation to just a String identifier, and leave the interpretation to relevant TestRunner implementation (which is already the case?)

(b) be able to pass optional params at testRunnerAdapter.test(...), so that they are transmitted to container side as additional hints. Map<String,String> would be good enough.