New parameters /C, /L and /A=

 *        - adds command /C to display current configuration
 *        - adds command /L to configure logging interval and parameters
 *        - adds option for command /A to set 24h average parameters during runtime
 *        - adds special parameter 20002 for logging /A command (24h averages, only makes sense for long logging intervals)
 *        - bugfixes for logging DS18B20 sensors