general class handling individual events
initialize the AppEventsHandler
container for an event payload.
name = name of the event, to which applications will subscribe. payload = dict of the contents of the event (key:value) **kwdargs = key:value pairs
either payload or **kwdargs should be used, not both
initialize the AppEvent contents
access points for subscribing to application wide events. timeout = 0 for no timeout
initialize an event notifier by name, with an optional timeout