Added interactiveMode='rebuildAndRestartOnKeyPress' support

Hi, I've added a new interactiveMode: rebuildAndRestartOnKeyPress. It will be usefull for setups with disabled source scanner like mentioned in #75.

This interactiveMode cannot be used in tasks that's depends on StarterLauncher as there's no dependency on gradle-api in gretty-starter project (and it shouldn't be as far as I know). But I think this won't be a problem because that tasks aren't interactive anyway.