Token hiding
Wrap testVisibility in order to hide a token based on elevation.
Given one or more points of vision to a token:
- test for intersection with an Enhanced Terrain Layer polygon.
- Test if the token can be seen from the point(s) of vision, assuming 3-D elevation for the token, wall, and point(s) of vision.
- Hide token as necessary
Also adds a log debug flag using the devMode module, and currently sets a debug flag to visualize the terrain polygons and intersections.