Updated version of agentscript, and modified return type of DataSet.slopeAndAspect().
Started using an agentscript DataSet to keep track of slope as water levels change.
Merge branch 'master' into droplets
Merge pull request #21 from bennlich/droplets

Preparing for droplets
example of Genesis-type vegetation population
center map in Taos; add color gradient lib and improve patch rendering;
fix bug where callbacks arent cleared when a layer is turned off
add elevation model
add elevation model
fix bugs
fix transfer function to disallow control points from overlapping
Fixed broken indentation.
Fixed transfer function bug, changed text fill, and added show/hide functions.
Added water velocity transfer function to flow model, and add show/hide to DataModels to turn corresponding interfaces on/off.
Forgot an absolute value (which surprisingly didn't seem to matter)..
Merge pull request #23 from bennlich/flowrate

WaterModel velocity now based on transfer function of slope
transfer functions for vegetation density
allow begin/end points to move in transfer function; set max elevation to 4000m
add default values to transfer functions
hide layers ui when editing