Change getState semantics

Currently Channel's getState method returns boolean indicating only whether state was successfully received by state receiver and not whether it was successfully processed at relevant channel listener. This anomaly lead to convoluted application code that had to do rather complicated lock synchronization and notification mechanism on the progress of entire state transfer.

We have to simplify this process! State receiver should simply call blocking getState and be notified in the form of Exception of anything that went wrong; be it that state could not be received at all or that it was received but could not be installed at channel listener.