Add checks from Maps.me subway validators

[nlehuby]

source code: https://github.com/mapsme/subways

Here is the list of checks. Some may already exists in the default JOSM validator, in PT assistant, etc

• "Stop area has multiple stations".

• "Tracks in a stop_area relation"

• "Only exits for a station, no entrances"

• "No exits for a station"

• "Stop position is not a node"

• "Not a stop or platform in a route relation"

• "Multiple stops for a station in a route relation"

• "Cannot find nodes in a railway". Detects broken OSM ways with 0 or 1 node.

• "Stop is nowhere near the track"

• "Public transport version is 1".

• "Ambiguous station in route. Please use stop_position or split interchange stations". This happens if a station object (i.e. a railway=station, not a stop_position) is in a route relation, and this station is included into several stop_areas; or when there are multiple stations of the same transport mode in a stop_area.

• "Untagged object in a route". Occurs quite often, for example when all tags from a stop_position were transferred to another node but old node is kept in a route relation.

• "An under construction stop/platform in route". Though it's unclear to me whether under-construction features should be added to routes.

• "Missing station= on a feature". Requires that railway=station/halt object be tagged with 'station=subway/light_rail/monorail' or have '=yes’. ’train’ mode is silently assumed for railways.

• " is not connected to a station in route". Occurs when a stop_position/platform is not included in a stop_area or the stop_area is missing a station object.

• "Route has no stops"

• "Route has only one stop"

• "Angle between stops around is too narrow, degrees".
  A sharp twist of a route most probably indicates incorrect stops order.

• "Route has different network from master"

• "Incompatible PT mode: route_master has and route has "

• "Route in two route_masters"

• "Stop area belongs to multiple interchanges"

• "An empty route master. Please set construction:route if it is under construction"

• Warnings about different colour/ref of route and route_master

• Warnings about holes in rails

• "Subway entrance is not a node"

• "Stop position in a 'platform' role in a route"

• "Platform in a 'stop' role in a route"

• "Stop is too far from tracks"

• "Stop position is not on tracks"

• "Tracks seem to go in the opposite direction to stops".

[nlehuby]

#48 adds some checks on subway entrances

[nlehuby]

Poke @alexey-zakharenkov @biodranik @vng @rtsisyk
Following on weeklyOSM 585 opening note: We suggest to port these useful checks on subways to Mapcss when possible.
It will allow OSM contributors to see these errors in JOSM when they are actually mapping, and in some other compatible tools such as Osmose, Unroll, etc

Help is very welcomed ;)