Custom selection pixel buffer

[rhodges]

Currently we have a 3-or-so pixel buffer around a cursor when clicking on a MapService layer: this creates a bounding box to use for querying for features to report on. We also have an option to turn this off, and only query for 2D features that overlap the point clicked.

What would be REALLY helpful, would be to enable adjusting the radius of the buffer for point or line layers served via MapServer. If the radius of the buffer of the click matched the radius of the icon (for points), of half of the width of the stroke (for lines) then clicking on the visible feature would result in a hit without impacting more accurate (tight) buffers for selecting other layers -- this would reduce selecting features that the user did not intend to click on.