Change .livescript and .livecode in file names to custom file type when building the app.

[Tonaras]

It would be a great feature if we could change the file types from "MyApp.livecode" and "MyAppScript.livecodescript" to some thing custom such as "MyApp.abc" and "MyAppScript.xyz" in the final builds of our apps. I'm sure this could be accomplished with a few tweaks in Levure, but I don't feel confiden enough yet to lay hand myself into the core Levure library, as this would also be dangerous when updating Levure etc.

What do you think?