It's easy to misspell `-Dlogback.debug=true`. When you use that property and nothing shows up in the log, it's impossible to easily see if there is no logging configuration (so the default is used) or if you misspelled it or misused it (for example used `-Dlogback.debug=true` as a program argument instead of a vm parameter).

If there is no logging configuration with `-Dlogback.debug=true`, output something like "No logback configuration found, using the default config instead".