Fix:xml:Fix bike routing

[mvglasow]

This improves bike routing (see also #844):

• Oneway restrictions are respected for bikes (if a way has different oneway restrictions for bikes, create two ways, one for each direction, and set access flags accordingly)
• Trunk roads are allowed if access flags permit, but with a low priority
• Unpaved paths get a low speed and priority so paved paths are preferred
• Priority decreases as road order increases

Tests with the use cases in #844 show significant improvements over the previous situation. There may not be a perfect solution because:

• We do not have elevation information so we cannot consider that for routing.
• We do know if a way where both pedestrians and bikes are allowed is segregated (we would prefer segregated ways for routing), or if a designated bike path runs right next to a main road (which some bikers might not like)
• Finding an easy-to-follow route is not always easy as most road networks are structured primarily with cars in mind, not medium-distance biking (and we do not have medium/long-distance bike path information in the map data, so we cannot consider that)

All of these would require a different approach to routing, primarily a cost function which does not solely depend on vehicle profile, item type and distance.

[mvglasow]

Fixes #844.