* Refactor WebPoller to remove "LongPoll" flag and "PollDuration" configuration. Replace
  concepts with "InterRequestDuration" setting that determines the amount of time between
  one request completing and the next request starting.
* Add "InterErrorDuration" setting that determines the amount of time between
  one error and re-attempting the next request.
* Add WebPoller.setLogLevel() method to make it easier to debug WebPoller.