Added Color Picker plugin
Point, Flicker and Pulse light animation should now look almost exactly as seen in GZDoom.
Fixed a bug when editing thing properties in Visual mode didn't update visual thing.
Fixed incorrect doom-style walls shading when sector has "lightcolor" property set.
Fixed "Index was outside the bounds of the array in CalculateNormalsAndShading()" error.
GZDoomBuilder will now show error message prior to failing.
