Big change-- Xbee now using softwareSerial

No need to use hardware serial for Zigbee. It was found that using
SoftwareSerial.listen, you can switch between two soft serials. In
addition, a higher baud rate counterintuitively unscrambled output from
the Xbee module.

Time for another bug fix: Using fixed size char array rather than
String. Reports using string class is buggy and can lead quickly to
memory failures, which is most likely what is happening now. Will have
to seriously change getxbee code and also packet structure.