global notification handler are like global event handler. They are fired each time
a notification would be sent out (regardless whether there is a contact or not)

    global_host_notification_handler=somecommand
    global_service_notification_handler=somecommand

global notification handler work like normal notifications, except they don't have contact
related macros set.

the global notification handler adds quite some noise to the log file, so
make it possible to disable it.

This generic LOG command can be used to add entries to the main logfile. It is
useful ex.: from a global notification handler to log the actual notified contacts.

align constants with spaces