Cleaning up more airframes
Add FrSky X9D + X8R/SBus
[ground_segment] settings: display ? on undo

should solve first part of #1054
[paparazzicenter] fix GLib-CRITICAL warning when running clean/build/upload

The func of the HUP io watch returned false, meaning the event source was automatically removed.
This resulted in trying to remove a non existent source in the callback, which is bad as the id could already refer to something else...
And of course this was resulting in highly annoying warnings on every process that is automatically stopped/removed (like clean/build/upload):
GLib-CRITICAL **: Source ID xxx was not found when attempting to remove it

So by simply returning true to not automatically remove the event source this should be solved...
Merge branch 'master' of https://github.com/paparazzi/paparazzi into openuas_working_tested_airframes
adjusted VVFMK1 n flightplans