+act #13004 Adding TailChopping router

Initial implementation + test for #13004
Does it look ok, or some generalisation with ScatterGatherFirstCompletedRouter should be made instead? 
I will update doc when final solution will appear.
Huh, that lack of termination was really silly mistake :/
I've added akka.pattern.after that terminates if timeout occurs.
As for cycles: for example, temporary network failure can happen, and sending more than once to each routee can be desirable? And mainly, I've done it as it was suggested by @ktoso in #13004. Should it be changed to not allow cycles?