Include nothing before Audacity.h, as comments say we should...

... and remove some duplicated inclusions

src/commands/ScriptCommandRelay.h

@@ -17,6 +17,7 @@
 #define __SCRIPT_COMMAND_RELAY__
 
 #include "../Audacity.h"
+
 #include "../MemoryX.h"
 
 class CommandHandler;