Use relations to improve access tags

[MoKob]

Access tags are not necessarily the only way to deduce bicycle access from. On some routes, relations might give insight into allowed access patterns.

For example https://www.openstreetmap.org/way/53191864#map=17/24.83799/-80.77334.

The oversees highway does specify access=all but does not specifically include bicycles.
It is however part of the relation https://www.openstreetmap.org/relation/4264361 which is part of the bicycle network.

Using relations, we could infer access tags for bicycles.

Related: #482