Changes to allow msbuild to build installers

No idea why, but manipulating CONFIG inside the build file confuses
msbuild command line builds. Work fine if you build from the IDE!

qgroundcontrol.pro

@@ -36,14 +36,6 @@ linux-g++ | linux-g++-64 {
     error(Unsupported build type)
 }
 
-# Installer configuration
-
-installer {
-    CONFIG -= debug
-    CONFIG -= debug_and_release
-    CONFIG += release
-}
-
 # Setup our supported build flavors
 
 CONFIG(debug, debug|release) {