Sanitize track URLs before logging?

[adamcik]

mopidy/mopidy-spotify#110 (comment) made me realize that we should probably strip out any auth info in URLs we log. I don't think we can ensure that plugins don't screw this up, but we should probably make sure core does it's part. One option that comes to mind is having a dedicated type that also does this sanitation when __str__ is used on it, forcing the cases where we want to true value to call some other method.