In Winter Field Day, accept DX as a section for DX stations and add DX to section in CAB file

[ny4i]

When working a DX station, accept DX as a section. The program will accept a blank which is OK but it should also accept DX as that is what the rules say to put there.

Also, when logging, if the section is blank and the station is DX, put DX as the section.

[ny4i]

This is a broader issue than the original bug. In testing, I noticed that one could enter just DX and it made that the class since it assumes DX as a section. The code needs to make sure we have a valid section for DX too for both Field Day and Winter Field Day.

When I do enter a class, the CAB file shows DX as the section ok so that seems to be working.

[ny4i]

I have a message into the WFD folks to check. ARRl FD doesn't matter since they do not check the logs anyway. It would be good to make sure the solitary entry of DX goes in the right place. If you just enter DX, it goes into the class and not the section. That should go in the right place.