Mapillary: Add new geo positioned object classes

[tordans]

Mapillary recently announced new object classes that are geo positioned like the traffic since we already have.

Announcement: https://twitter.com/mapillary/status/1088010250878361601

What would be a good UI to add those to iD?

[bhousel]

Nice! Yes I've chatted with @cbeddow about this. We'd like to improve iD's custom data capabilities and connect to these new sources like other vector data sources.

[cbeddow]

We had the idea of having the Mapillary data layer instead of traffic sign layer, where you could select a layer: traffic signs, points, lines then subfilter like by stop signs only, or trash bins only, or sidewalks only. Still open to UI ideas, though @bhousel and I had discussed using the modal window similar to what adding custom tiles brings up.

[quincylvania]

I believe the basics of this were done by @kratico in #6792. Please open new issues for any further work.