Removed invalid TestEventListener from FullDebugConfig in TestKit.

As TestEventListener is installed by default this is not necessary. And the line was invalid anyway.
Also updated docs to include full class name
Do not check if Current is set before setting TestActor as implicit sender

The check messed up tests that were run consecutively, as the second test would not set TestActor as sender.
Merge pull request #420 from HCanber/testkit-implicitsender-bug

Fixes Testkit implicit sender bug & FullDebugConfig-bug