[Tagging] route/forward/backward members in all types of routes

[Georg Feddern]

Am 10.01.2018 um 12:32 schrieb Ilya Zverev:
> Selfish Seahorse wrote:
>> The course of the route is determined by the order of the stops in the
>> route relation. Therefore forward/backward roles would be redundant.
> But stops are not mandatory in public transport routes, unlike highways/railways!
I am quite sure that in _reality_ a stop _or_ a platform is mandatory in 
a public transport route - otherwise you would just have a route with 
'hitchhiking'?
PTv1 - zero or more for both - aha ...
PTv2 - mandatory for both, but if may be only one is present, the other 
is not really mandatory anymore - aha ...

There is a reason for that I only map highway=bus_stop ...