Support scanning a directory for log4j2 configuration files

New property _log4j2.configurationDirectory_ would work similar to the comma separated list in _log4j2.configurationFile_ where multiple configuration files can be used for an application.

This behavior would allow dynamic loading of configuration files, instead of requiring the name of each configuration file ahead of time, which is the case with _log4j2.configurationFile_.

1. If property _log4j2.configurationDirectory_ is set, recursively scan the directory for matching configuration files.
2. Limit directory depth to something reasonable (16 or so by default)