add settings icon,

set ogl verison to 2.0 to make it compatible with more PCs

QtMeshViewer/Resources/Resources.qrc

@@ -26,5 +26,6 @@
         <file>X_disabled.png</file>
         <file>Y_disabled.png</file>
         <file>Z_disabled.png</file>
+        <file>settings.png</file>
     </qresource>
 </RCC>

QtMeshViewer/Resources/StyleSheet.txt

@@ -71,6 +71,10 @@ QToolButton#light:checked {
 	image: url(:/images/toolbar/light_on.png);
 }
 
+QToolButton#settings {
+	image: url(:/images/toolbar/settings.png);
+}
+
 QToolButton#fileInfo {
 	image: url(:/images/toolbar/info.png);
 }