Tons of little changes...

Lots of little changes today, made while working on something else:
*  Add a "isNumber" function to the funcs file.
*  Added several options to the ArcGIS vector layer class.  It now
supports vertical exaggeration, user defined geometry generation, user
defined z values, and z values provided as part of the geometry.
*  Also added support for the "simple" point symbology type, where
everything has the same symbol.  It actually supported this already, but
I cleaned the code up so it has its own code path.  Should be easier for
other developers to understand.