Add classpath to --thin.debug=true

[odrotbohm]

The thin launcher's main responsibility is to resolve dependencies to run a Boot app. That means, the actual binary doesn't contain them in the first place. Thus it would be cool if the application could be run and the resolved dependencies were logged prior to the actual application's run.

A couple of options to see the classpath already exist, with a couple of downsides:

• --thin.classpath — doesn't run the app
• -Ddebug — switches on Boot's debug mode which actually lists the classpath but also enables verbose output for the entire app (autoconfiguration report etc.) which might be too verbose for a production run

It would be cool if -Dthin.debug included the calculated classpath (essentially what --thin.classpath outputs but maybe a single line per dependency for easier grep-ing?).