Serialization, DebugLogger tweaks

* Tweaked ServiceStackJsonSerializer to serialize/deserialize DateTime
values via the To/FromBinary methods, in order to get exact values in
and out. Otherwise, it was trimming off picoseconds (or whatever).
* Added simple DebugLogger static functionality to make it easier to
Start/StopListening. Just need to call DebugLogger.Start/StopListening.
;)