add UI to pick min/max band values in histogram

Author: etiennesky

images/images.qrc

@@ -389,6 +389,7 @@
     <file>themes/gis/mActionTouch.png</file>
     <file>themes/default/mActionAddMssqlLayer.png</file>
     <file>themes/default/mActionTouch.png</file>
+    <file>themes/default/mActionTouch2.png</file>
     <file>themes/classic/mActionTouch.png</file>
     <file>flags/af.png</file>
     <file>flags/ar.png</file>