Experimental script to generate a ground network for default airports
Works on all airports which have the following 810 format: one runway,
one long taxiway along the runway, 3 short taxiways to the ends and the center
of the runway. 9 parking positions are also generated near the long taxiway.

First set path in the script to the Airports directory inside the scenery directory.
This can be obtained with Terrasync.
Ground networks will be saved in the output directory inside the current directory

After the first run, a cache file named airport_list.txt or airport_list_850.txt
is created in the working directory, containing a list of all airports in the scenery
directory which are missing a ground network, regardless of the format of the airport.
This makes further runs of the script execute faster.

Version 0.2: The script now can parse v850 airports which fit the same default
format. To use the 850 parser you need a apt850.dat file in the working directory.
Ground networks will be saved in the output850 directory inside the current directory

Usage:
groundnet.py all 			#-> generates all airports which fit the criteria
groundnet.py airport <ICAO> 		#-> generates only one airport for the ICAO code provided

groundnet.py all 850 			#-> generates all airports from apt850.dat which fit the criteria
groundnet.py airport <ICAO> 850 	#-> generates only one 850 airport for the ICAO code provided