Add custom POIs and speedcams

[ZeljkoBG]

Since I became
"... now a member of Organic Maps!"

New idea:
Allow speedcams to be added to the app. OSM maps have Speedcams whose base is minimal and inaccurate.
Connect with https://openspeedcam.ne they have the best database of speedcams.
Allow adding your own POIs with your own icons.