Module scheduler stats (file and socket)

Get stats of scheduler for each poller (poller_tags have to be configured)
possibility to change timing (var history) in scheduler.py

USAGE :
specify your configuration in shinken-specific.cfg
(path to file for write_file &
ip/port for socket_write)

	modified:   ../etc/shinken-specific.cfg
	new file:   ../shinken/modules/send_socket_log.py
	modified:   ../shinken/modules/write_file_log.py
	modified:   ../shinken/scheduler.py