api: Extracted common parse_location() function
api: Simplified MWP api output

.. also API output shouldn't use i18n functionalities!
api: Added wave_to_json() function
api: Added airspace_to_json() function
api: Use map() for JSON conversion
model/geo: Added to_wkt_element() method to Location class
model/geo: Added make_point() method
model/geo: Added optional srid parameter to to_wkt_element() method
model/airspace,waves: Use faster make_point() instead of to_wkt_element()
api: Import cleanup
model/airspace,waves: Renamed get_info() methods to by_location()
api: Moved parse_location() calls into route handlers

Only parse location once for '/' route
api: Moved combined map item query to /api/mapitems
model/geo: Added Bounds class
model/airport: Added static by_bbox() method
model/geo: Added ValueError descriptions
model/geo: Check that latitude values are valid
model/geo: Added get_width/height/size() methods to Bounds class
api: Added /api/airports route

This route can be used to query for all airports in a certain bounding
box or the details of an airport with a certain id.
api: Added @jsonp decorators