[Tagging] service=yard - changing definition on wiki from "marshaling yard" to "railway yard"

[Mateusz Konieczny]

service=yard is widely considered as to be used to tag tracks in
"complex series of railroad tracks for storing, sorting, or
loading/unloading, railroad cars and/or locomotives".

But Wiki currently defines service=yard to be used only for marshaling
yards ( http://wiki.openstreetmap.org/wiki/Tag:service%3Dyard ) -
narrower term. Marshaling yard is a type/part of railway yard - used to
separate railroad freight cars on to one of several tracks

Maybe that was initial tagging and it would probably stay this way with
self-documenting tag (service=marshaling_yard) but as tag was much more
general than its definition it is now used to tag any kind of railway
yard (up to and including tram depots).

I propose to change on
http://wiki.openstreetmap.org/wiki/Tag:service%3Dyard "marshaling yard"
to "railway yard" to document current tagging.

Overpass query, starts centered on tram depot with service=yard:
http://overpass-turbo.eu/s/9p8