GUI: Change default color map (#273)

An approximative solution to #273 (closed).

GUI/Model/Data/IntensityDataItem.cpp

@@ -38,7 +38,7 @@ ComboProperty gradientCombo()
            << "Spectrum"
            << "Jet"
            << "Hues";
-    result.setValue("Jet");
+    result.setValue("Thermal");
     return result;
 }