Add "tapTolerance" configuration option for mobile devices

When drawing editing using a Stylus on a tablet drawing on a map is diffiult.  The Geocortex library seems to treat the pen as a mouse event rather than a touch event, so if there is the slightest movement, even by a single pixel, the library registers it as a drag.  The Leaflet library has a “tapTolerance” value that allows for a pixel value to be set, where any shift less than that number is considered a click instead of a drag.  A similar tolerance for Geocortex would make it more usable for mobile devices.