Add support to maxspeed:forward and maxspeed:backward

[muralito]

Please add support to tags "maxspeed:forward" and "maxspeed:backward", in the sense of equivalence with "maxspeed", or at least to colour the way with the same blue that is used when "maxspeed" tag is present.

[k1wiosm]

Motorways are oneway, so I would think that they would not have maxspeed:forward or maxspeed:backward tags. Can you show me an example of a motorway that uses them?

[muralito]

Hi. Yes, motorways are always oneway, but i used to use your software to check also other types of ways, such as trunk or primary, so not always are oneway.