Allow features to be disabled at build time (#143)

* Add framework for built-time feature selection
* Allow MQTT, NTP, OTA features to be disabled at build time
* Allow Project screens to be disabled at build time
* Allow security features to be disabled at build time
* Switch to std::function for StatefulService function aliases for greater flexibility
* Bump various UI lib versions
* Update docs

lib/framework/APSettingsService.h

@@ -96,4 +96,4 @@ class APSettingsService : public StatefulService<APSettings> {
   void handleDNS();
 };
 
-#endif  // end APSettingsConfig_h
+#endif  // end APSettingsConfig_h