Use consistently the gml:id prefix "uuid."

Use consistently the gml:id prefix "uuid." instead of mixing "urn.uuid." and "uuid."

AIXM Feature Identification and Reference 1.0, page 7:

> It is recommended that the gml:id of the AIXM features (such as aixm:Airspace, aixm:Runway, etc.) also make use of the UUID value, prefixed with "uuid.".

http://www.aixm.aero/gallery/content/public/AIXM51/AIXM_Feature_Identification_and_Reference-1.0.pdf#page=7