Discourage access=destination, access=customers

[graue]

I got a route that clownishly uses the Flower Mart parking lot to avoid a mixing zone on 5th Street:

This passes through a gate with access=customers set, which, along with access=destination, we should preferably not use for through traffic. We can approximate that by weighting the way as REACH_DESTINATION.

The easier subtask which wouldn't help in this specific case would be to weight ways with access=customers or access=destination (or the equivalent values more specifically for bicycles, e.g. bicycle=customers) that way. (Currently, it looks like those values of access aren't considered for bicycle routing at all.) Likely more complicated is to take into account the barrier=gate with those access values as well.