VSC100 OS

Fixed SDI-12 "C" command as it was not always responding.

Changed Modbus register scheme so it now conforms with the Modbus standard where (2) 16-bit registers make a floating point value. Previously requesting the value of (1) register would return (1) floating point value.

Added Modbus error code when attempting to read from Modbus registers outside the allowable range of readable registers.

Added Modbus error code when attempting to write to Modbus registers outside of the writeable range.