COMMONS-344 [UserStateService] ping REST service returns 403 error in public mode
SWF-2923 : Create pkg-improv branch and update projects versions

Signed-off-by: Arnaud Héritier <aheritier@exoplatform.com>
PLF-4469 : Import ExtendedPropertyConfigurator class from platform-cloud (https://github.com/exoplatform/platform-cloud/blob/master/services/src/main/java/com/exoplatform/platform/container/ExtendedPropertyConfigurator.java) to allow to load additional configuration files (configuration.properties with default properties and exo.properties with user settings)
PLF-4469 : Customize ExtendedPropertyConfigurator to not let ContainerUtil.loadProperties display an error in logs if the file isn't found (${gatein.conf.dir}/exo.properties won't be provided by default)
PLF-4469 : Load user configuration from ${gatein.conf.dir}/exo.properties if it exists
PLF-4469 : configuration.properties must be loaded from classpath (platform-extension-config-VERSION.jar) to get default settings
PLF-4469 : jbosscache and jgroups configurations must be loaded from classpath (platform-extension-config-VERSION.jar)
PLF-4469 : remove useless configuration.properties entries about logs
PLF-4469 : remove useless comment in configuration.properties
PLF-4469 : Cleanup configuration.properties and allow everywhere it is possible to define properties from system properties
PLF-4469 : exo-sample.properties is provided to users to easily create an exo.properties file to override values defined in configuration.properties
PLF-4469 : Useless comment. It is only an internal file now
PLF-4469: (EXT_PLAT_CONF_09) Add new properties and define default values of existing ones from cluster/jgroups/jbosscache in configuration.properties
PLF-4469: Reorganize properties files and add cluster config in exo-sample.properties
PLF-4469 : Reformat config files
PLF-4469 : Rename cache.cluster.* properties to exo.cache.cluster.* to be coherent with the Simplified Cluster config spec
PLF-4469 : Rename jgroups.protocol -> exo.cluster.transport
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