Add "ref" field for bus stops

[lest69]

I've seen several users putting bus stop "ref" numbers into the name, which is an incorrect and unhelpful misuse of the tags. If a field for the ref number could be made available when adding or editing a bus stop, this would help discourage misuse of the "name" tag.

[jaller94]

In Vancouver, BC bus stop numbers which where put in the name and name:en field are a regular issue too. Those changesets indicate that Maps.me was the editor used.