menu positioning for the plugins works now

menu positioning for the plugins works now

example:
def getMenuRegistrationList():
	list = []
	list.append(("setup", 2, "Softwareupdate", "Example"))
	list.append(("mainmenu", 0, "Foo", "Bar"))
	return list

this means, that we have 2 menu entries:
a menu entry "Softwareupdate" is added to the setup menu on position 2 which calls the Example screen of the plugin
and a menu entry Foo is added to the main menu on the first position which calls the screen Bar