Add node collection from Overpass

[vroom-project]

Add node collection from Overpass

[jcoupey]

This would be a great way for users to easily design relevant problems without any programming/formatting skills, especially in the light of the current situation.

I'd be happy to take part in the associated dev and push this to http://map.vroom-project.org/ as soon as it's available.

[jcoupey]

Couple notes on the technical side:

1. I'm not sure we'd really need a reverse geocoding step. Currently a click on the map triggers one because it's a way to use the address as a job description. But Overpass results would most of the time yield a name tag that would be even more relevant.

2. There is a limit on the total number of jobs that can be added through the frontend that reflects the limitation on the demo server. We'd have to deal with that, either by limiting the number of results retrieved from Overpass to the number of remaining jobs, or by checking against the total number of jobs upon additions.

[jcoupey]

This landed with #50 and is now live at http://map.vroom-project.org/