Allow users to set surface preferences for routing

[samcrawford]

Users should be able to pick the surfaces they prefer.

Open questions:

• Should these be sliders? It will make the UI very busy.
• Should they be able to select multiple? Presume yes.
• What should the defaults be? "No preference" ?

[westis]

I don't think the 6-7 sliders suggested in #23 will make the UI too busy. Perhaps use the entire left side of the screen for the settings menu?

Rather than selecting multiple surfaces I'd suggest a slider from asphalt via compacted/fine_gravel to unpaved to ground to mud/clay/sand. The chart at https://groups.google.com/forum/?utm_medium=email&utm_source=footer#!msg/osm-android-bikerouting/5lEL-gbiqV0/KQAd-CgXAwAJ could give a hint on the weighting of each surface value depending in the slider.

However, there should also be a check-box for the user to activate the slider or not. If de-activated, surface is not at all considered in the route calculation. If selected, default is in the middle, which would probably be something between compacted/fine-gravel to unpaved.