Alpha release with new REP_watcher option, DHT11 & DHT22 sensor support and more PiCamera settings

This release adds a REP_watcher yaml option that checks for a timely REP after sending a REQ, removing the dependency on signal.SIGALRM, which does not work in Python threads. It also adds DHT11 & DHT22 temperature / humidity sensor support and many more PiCamera settings. See HISTORY.md for details.