PLF-4469 : Use only our ExtendedPropertyConfiguration to load the exo.properties and the configuration.properties. Everything in configuration.properties using ${prop:default} as value can be override in exo.properties
PLF-4469 : gatein.conf.dir cannot be defined here. It is used to find exo.properties. The gatein configuration directory must always have default files we provide in our distribution. They cannot be reorganized one by one
PLF-4469 : improve docs