AVL Reports don't display tiles because of Mapbox terms&conditions

[wkulesza]

Expected functionality
Each generated AVL reports should show vehicle positions over time on map.

Describe the bug
As map tiles are served by Mapbox, which is a paid service, map is not visible in the reports, with error in console:

	"message": "Classic styles are no longer supported; see https://blog.mapbox.com/deprecating-studio-classic-styles-d8892ac38cb4 for more information"
}```

**To Reproduce**
Open Reports, then AVL Data in Map by Vehicle and then generate a report.

**Screenshots**
http://prntscr.com/16knjlj

**Version:**
Newest development branch of transitime, being used by TC docker

**Configuration:**
Standard

[wkulesza]

Just to confirm, this code change does work and could be the solution:
camsys@2b40bdb

Would be better to allow this to be configurable though - to allow user to select which tile provider he prefers (if. mapbox, than token needs to be provided, if openstreetmap, then use the above code change.