Donlon version 1.1 from AIXM Wiki

Imported from:
https://extranet.eurocontrol.int/http://webprisme.cfmu.eurocontrol.int/aixmwiki_public/bin/viewrev/Main/%5BDonlon%5D%20Baseline%20data?rev=1.1
Donlon version 2.1 from AIXM Wiki

Imported from:
https://extranet.eurocontrol.int/http://webprisme.cfmu.eurocontrol.int/aixmwiki_public/bin/viewrev/Main/%5BDonlon%5D%20Baseline%20data?rev=2.1
Donlon version 3.1 from AIXM Wiki

Imported from:
https://extranet.eurocontrol.int/http://webprisme.cfmu.eurocontrol.int/aixmwiki_public/bin/viewrev/Main/%5BDonlon%5D%20Baseline%20data?rev=3.1
Donlon version 4.1 from AIXM Wiki

Imported from:
https://extranet.eurocontrol.int/http://webprisme.cfmu.eurocontrol.int/aixmwiki_public/bin/viewrev/Main/%5BDonlon%5D%20Baseline%20data?rev=4.1
Donlon version 5.1 from AIXM Wiki

Imported from:
https://extranet.eurocontrol.int/http://webprisme.cfmu.eurocontrol.int/aixmwiki_public/bin/viewrev/Main/%5BDonlon%5D%20Baseline%20data?rev=5.1
Donlon version 6.1 from AIXM Wiki

Imported from:
https://extranet.eurocontrol.int/http://webprisme.cfmu.eurocontrol.int/aixmwiki_public/bin/viewrev/Main/%5BDonlon%5D%20Baseline%20data?rev=6.1
Donlon version 7.1 from AIXM Wiki

Imported from:
https://extranet.eurocontrol.int/http://webprisme.cfmu.eurocontrol.int/aixmwiki_public/bin/viewrev/Main/%5BDonlon%5D%20Baseline%20data?rev=7.1
Donlon version 8.1 from AIXM Wiki

Imported from:
https://extranet.eurocontrol.int/http://webprisme.cfmu.eurocontrol.int/aixmwiki_public/bin/viewrev/Main/%5BDonlon%5D%20Baseline%20data?rev=8.1
Various improvements
Add LICENSE and README.md
Update LICENSE
Update README.md
Fix missing gml:identifier in a VerticalStructure