use destination tags/relations for instructions

[emiltin]

destination tags and relations are intented for providing better instructions in navigation apps, by providing info about signage that can be followed.

http://wiki.openstreetmap.org/wiki/Key:destination
http://wiki.openstreetmap.org/wiki/Relation:destination_sign

(not be be confused with access=destination)

[MoKob]

closing in favor of #2267