allow disabling build-time logic

[Roguelazer]

I'd like to use this library, but have all of the current-version logic handled somewhere else; I don't want it to write a VERSION.txt, nor to populate currentVersion in the built app. It seems like there's no way to do this without explicitly setting APP.version to null, which has other side-effects. What would you think about adding a config value or special sentinel value for config.currentVersion which would disable this logic.

[knownasilya]

Sounds like a good idea.