Design of base components + Clock

* Code improvement
* Clock implementation
* Tests
* License headers
Note sure that using logging this way scales with the number of messages as ${frequency.toNanos} and the string interpolation will have to be applied whenever the debug method is invoked (even if the debug mode is not activated). Why don't we use the placeholders described in http://doc.akka.io/docs/akka/2.0/scala/logging.html ?