add support for IGC format

[efa]

IGC files are generated by Flarm, LXnav instruments, Colibrì and others. Are waypoints files. Can be good support at least as input, best would be output too. GPSbabel manage them: $ gpsbabel -i IGC -f 2016-04-24_Valerio.IGC -o CUP -F 2016-04-24_Valerio.cup Will provide some example files and documentations on format