Add -Dapp.config property to scripts

[leif81]

Since configurationDirectory is configurable in the goal, it would be useful to pass this value through the app launcher scripts just like app.home, etc get passed.

e.g. a property like this on the jvm line of the generated script:

-Dapp.config=etc

And then at run time the user can grab the app.home + app.config to resolve the path to their configuration files.