make sensor/turnout default username

[balazsracz]

IN JMRI, when the user clicks make sensor or make turnout, the username is filled in by default from the description field. If it's empty, the username is left empty.
It would be better to fill the user name with some default identifier, probably computed from the CDI xml stuff, like:
node username - group name - repname rep.number

[pabender]

I don’t believe this is a valid issue for OpenLCB.

We can’t do anything in the OpenLCB library to force this to happen unless we also force other Java applications using the library to have the same behavior.

[balazsracz]

​JMRI is using an API to achieve this functionality. I don't remember the exact split of responsibility between the two codebases. You may be correct in that it's possible this change would only touch JMRI code; but it's also possible that we might have to revise the API slightly.