Add a comparator for degraded cycle access

[rskedgell]

I frequently see cases where a highway=cycleway is changed to highway=footway or highway=path without adding an appropriate bicycle=* access tag, breaking cycle routing.

In some cases, this is absolutely correct, but should probably still be flagged for review. If the way is part of a bicycle route relation, it should always be flagged.

In some cases, these modifications are unwanted tagging for the renderer and are accompanied by changeset comments referring to "pedestrian priority". In the UK at least, this is a misunderstanding of what the tagging means: pedestrians always have priority on shared use cycle tracks (Highway Code Rule H3).

In a minority of cases, degrading cycle access is malicious and done as a result of NIMBYism or trying to vandalise the map to reflect the desires of the mapper rather than the reality on the ground.

[willemarcel]

It's really a good suggestion, @rskedgell