completely remove rulesChangedObserver, see commit fbc365c
coding style (and indentation) changes

in overlay.js, menu.js and classicmenu.js
report catched errors to the browser console
move bootstrap-manager to jsm file
create startup and shutdown functions in bootstrap-manager
coding style changes (bootstrap-manager)
BootstrapManager: introduce startup/shutdown function stacks

From now on any module registers its startup/shutdown function(s) by itself,
so the BootstrapManager doesn't have to care about this anymore.
fix a bug with Australis. fixes #532
implement "new tab behaviour"

resolves #488 and fixes #531