Currently logging configuration is splitted in two distinct classes,
the api.pp and the logging.pp classes. This review aims to centralize
all logging related parameters in a single class, the logging.pp one.
The impacted parameters are :
* use_syslog
* use_stderr
* log_facility
* verbose
* debug
* log_dir
* log_file
This change remains backward compatible with what is currently in place.
Change-Id: I6e56123217a38c384734d31e60699f7b76f7dc4a
c4efae01d7