Better ways to interact with Mapillary photos

@ajithranka is already working on this.

Since Aug 29, 2016.

As highlighted during the [shadow exercise](https://github.com/mapbox/osm-navigation-map/issues/63#issuecomment-240395778) with @srividyacb, the Mapillary photos play a major role in mapping & verifying turn restrictions. Making even minor improvements to the workflow should add up to make a significant difference.

Based on the discussion with @ajithranka & @planemad here are a few things that we need to relook/explore:
1. Visually differentiate Mapillary `object` (estimated location of the signage), Mapillary `signage images` (that detect the specific signage/object), and remaining Mapillary images & trails — @rasagy to design icons
2. Show icons on the Mapillary `object` — @planemad to hook up the sprites shared in #38 in the map style
3. Show the `bearing` for the Mapillary `object`
4. Rotate icons for Mapillary `signage images` and remaining images using `bearing` property — @ajithranka to experiment with data-driven icon-rotate property
5. Navigate through images in a particular trail — @ajithranka to build a UI using Mapillary.js to move to next/previous image in the trail
6. _Explore_ more ways to interact with the thumbnail: Using the bounding box (rects) for detected signage in the image, alternate ways to pan/zoom etc. — @ajithranka & @rasagy to explore and build an experimental prototype
7. _Explore_ swapping map & image thumbnail view to let the reviewer focus on the images with the map shown as a small thumbnail to just highlight where the images are — idea to explored by @ajithranka & @rasagy (low priority)

@ajithranka & @planemad, can you add anything else that I might have missed?