Adding speed camera's to Surveillance theme

[thibaultmol]

I'm not sure what the right solution is but for 'traject controles' (average speed speed camera setups) they use camera's that do both license plate recog and speed detection but it's not possible with the theme to actually correctly get a highway=speed_camera tag on an object.

(also fiy: there seems to be a tagging scheme thing where speed camera's have a different orientation tag than normal surv camera's. Speed cam uses direction= while regular surveilance cams use camera:direction=)