Artnet short name change

[elektroservis]

solved

[claudeheintz]

In order for the library to run on an Atmega328 (Uno) the long and short names are stored in an array that holds the contents sent as a poll reply. A pointer to this array is accessible with replyData(). However, I just added shortName() and longName() which provide pointers into the poll reply array at the correct indexes to make things easier. (Also, I added setting the long and short names remotely with an artAddress packet)