[2.0.77] Allow LuaEntities representing train stops as elements in AddRecordData

[hgschmie]

There are two ways of adding new records to a train schedule: a specific rail (LuaEntity), maybe refined with rail_direction or a train stop name. The former allows to exactly pinpoint where a train should go, the latter tells the train "find any station with that name and go there".

It should be possible, in addition to those to do station = <lua entity that represents a train stop>. This would combine those two things: Pinpoint a specific station and send the train there. Basically a combination of having a temp stop with the rail attached to the station and the station name (which is what e.g. LTN uses to schedule trains). Given that pinpointing a rail is already possible, why not allow pinpointing a station as well?

(bonus points for allowing stations on different surfaces. )