Modified handling of ISEC.txt
Created some logics for the handling of the ISEC.txt
Now it does NOT need to be shared with the dll, as it will simply search the NAVDATA folder
ATTENTION! This means that the .dll needs to be on [YourSector]\Plugins\EuroNat folder, as for now this is how I set up the logic
By doing so, it will automatically copy the GNG ISEC.txt that comes from the [YourSector]\NavData folder!
If it doesn't find it anywhere, it will warn the user about it
Created a box between 30N and 90N, 70W and 1W for searching the waypoints on the ISEC.txt
This should solve the issues of the first waypoint found not being relevant for the NAT tracks common airspace