Fixes to the devcomuino sketch

Improves the stability of the devcomuino sketch via the following:

• Check that the termination character is received before processing the command to ensure all data has been received.
• Correctly end the received data with \0 to turn it into a c-string.
• Remove the delay at the end of loop. This blocked the microprocessor.
• The termination character is set to \r\n, for consistency with the Serial output.
• cmdI2Cwrite now sends all bytes, instead of just one
• Switch SerialCom to use blocking communications.
• Remove debug output for help with parsing the output.

There is also an example called devcomuino_example that demonstrates how to use this sketch.