add "route" role unknown (to presets?)

[mkoniecz]

According to ​http://wiki.openstreetmap.org/wiki/Relation:route#Members empty or "route" role should be used for ways making up the route.

Currently using empty results in "Empty role found" and "route" in "Role route unknown".

Probably the second version should be encouraged and should not result "Role verification problem" warning from validator.