Layer tolerance default value

[jlacroix]

The tolerance default value in the layer is 0. This works well with polygon
layers since this value will return query result for a click inside the polygon.
However for line and point layers a tolerance of 0 seems always return nothing
(It's the like the layer is not queryable). In the documentation the default
tolerance is marked as 3, but in the code it's 0.

Should we update the documentation or update the tolerance value?
Steve?