[WIP] Add text instruction parsing via osrm-text-instructions

[freenerd]

First pass at integrating https://github.com/Project-OSRM/osrm-text-instructions.js

Todo:

• Find better way to integrate custom logic in leaflet-routing-machine
• Wait until https://github.com/Project-OSRM/osrm-text-instructions.js is stable and handles all possible cases
• Wait for https://github.com/Project-OSRM/osrm-text-instructions.js to be bumped to a stable-ish version
• Merge

[freenerd]

For comparison, here are old (left) and new (right) instructions side by side:

[freenerd]

osrm-text-instructions has made progress in the last weeks and feels fairly stable now. There are def more cases we want to support, but it's good enough for the basic case here. To get more feedback we'd love to get it live on map.project-osrm.org now.

I also continued on the hacky path to get lanes support in.

It's not pretty, but works a bit. The problem with integrating with LRM is that during the HTML building, I need access to the original step object from OSRM to decide on lanes. Since the other supported routing engines do not support lanes, Im not sure if this should become a LRM-supported function. If so, it will need quite a lot of refactoring on the LRM side.

Old Left, New Right

[freenerd]

I released osrm-text-instructions@0.0.1 which includes destinations as well, so I think it's ready to go for now.

@perliedman I'd love to find ways of getting this work upstream into LRM. Likely integrating osrm-text-instructions will be easy-ish, since it's only some text. But lanes are harder, since they need the original step.intersections.lanes while building the html. I couldn't find easy ways of integrating them, so need to defer back to you on that.

I'll merge this hacky version for now to get the feature out. Let's continue to discussion on how to make it better :)