Handle Output directory better

Git refuses to store empty directories.  So, build scripts modified to
create Output directory as needed.

Build.cmd

@@ -1,4 +1,9 @@
 @echo off
+
 setlocal
+
+if not exist Output md Output
+
 cd Source
+
 call Build %*

BuildImages.cmd

@@ -1,4 +1,6 @@
 @echo off
 setlocal
 
+if not exist Output md Output
+
 pushd Images && Build && popd

Clean.cmd

@@ -8,4 +8,4 @@ pushd Images && call Clean && popd
 if exist *.img del *.img /Q
 if exist *.log del *.log /Q
 
-if exist Output\*.* del Output\*.* /Q
+if exist Output rd /s /q Output