Allow an additional simplelogger.properties file.

Use case: We have a simplelogger.properties in the git-managed source tree. However, we also want to have a .gitignored properties file so we can do quick local testing.

Suggestion:

Add configuration directive org.slf4j.simpleLogger.configFile.
Includes the file, overriding the settings from the source that the configFile directive was in (simplelogger.properties or system properties, whichever may be the case).
The included file must not contain another configFile directive.

My status: Discussion welcome. Willing to contribute patch if so desired.