Added GUI for manual addition of comm frequencies for satellites (#2476)

This feature was added into TODO list (item: GUI for manual addition of comm frequences) for Satellites plugin at least 9 years ago, but it was probably earlier. I've added the GUI to adding and removing the communication data for individual satellites only - the tool doesn't support groups of satellites (this is intended behaviour!).

Co-authored-by: Georg Zotti <Georg.Zotti@univie.ac.at>