isocolors.m: Overhaul function. * isocolors.m: Rewrite docstring. Rename output to cdat, rather than varargout, for clarity. Rename variable "new_col" to "new_colors" for clarity. Verify that input handle is actually a handle to a patch object. Don't issue an error if there is more than one output variable. Add input validation BIST tests. * __interp_cube__.m: Change function prototype to accept accept a first argument caller. Prefix all error messages with the name caller. Change docstring to match new prototype. Simplify input checking by testing that only one of the input matrices has 3 dimensions, and then using size_equal to verify that they all must have 3 dimensions. * isonormals.m: Change calls to __interp_cube__ to use caller as first arg.

--- a/scripts/plot/draw/isonormals.m	Wed Nov 16 21:03:16 2016 -0500
+++ b/scripts/plot/draw/isonormals.m	Thu Nov 17 09:55:51 2016 -0800
@@ -100,9 +100,9 @@
   endif
 
   if (negate)
-    normals = __interp_cube__ (x, y, z, val, v, "normals");
+    normals = __interp_cube__ ("isonormals", x, y, z, val, v, "normals");
   else
-    normals = -__interp_cube__ (x, y, z, val, v, "normals");
+    normals = -__interp_cube__ ("isonormals", x, y, z, val, v, "normals");
   endif
 
   switch (nargout)