Provide additional imperial unit conversion option

[daniel-j-h]

As requested in

• https://lists.openstreetmap.org/pipermail/osrm-talk/2015-December/001082.html
• https://lists.openstreetmap.org/pipermail/osrm-talk/2016-January/001094.html

there should be an option for MPH conversion instead --- or better in addition --- to the default km/h.

/cc @amyleew what is your take on this? Is this something that could be easily and quickly done?

[perliedman]

Not to nitpick, but I don't think km/h or any speeds are shown anywhere - the issue is (as far as I understand), to show distances in miles rather than kilometers.

There's already an option in Leaflet Routing Machine to use imperial units rather than metric, so this should hopefully just be a matter of adding a UI to change that option.

[daniel-j-h]

Ha, correct. The MPH just came in because it was the mailinglist thread's topic.
Yes, an option to switch to imperial units is what this is about.