WIXFEAT4149 - Adding support to WixStdBA for displaying the message "Uninstall Successful"/"Repair Successful" after product uninstall/repair

Hello, we want you to present our "lightweight" implementation [WIXFEAT4149] (http://wixtoolset.org/issues/4149/). In the discussion on the wix-devs, you have not come to a consensus, or discussing labor-intensive solutions. This implementation is easy to develop and support, because it requires minimal modifications as WixStandardBA as themes.