Type conversions.

[MatthewHink]

This is for the work on the busway.

Mac Addresses:

• Often a mac address is just a six length byte array.
• The busway uses six uint16s which is 12 bytes. (A function of modbus 16 bit register data)
• Added conversion to string of the form 01:02:03:04:05:06

Some data appear to be non-null terminated strings which I am not sure what to do with. For now we can leave them as byte arrays.