some setters return self reference, Url::toString() method was renamed to toStr()
bug fix: base64_decode() sanity check for 'd'
DeviceHive framework refactoring:

- common interface for Restful and Websocket services!
- automatic (Restful->Websocket) service switching in examples
- Command and Notification should be used via shared pointers
- no more example duplication (Application & ApplicationWS)!
- DelayedTasks was split into two classes: DelayedTask and DelayedTaskList
ping/pong timeouts

(10 seconds idle timeout, 5 seconds pong timeout, 3 attempts)
now ping/pong timeouts are disabled for a while because server doesn't support ping/pong frames yet