Bug 916709 - Implement PopupWindow (v4)

Conflicts:
	apps/system/js/activity_window.js
	apps/system/js/activity_window_factory.js
	apps/system/js/bootstrap.js
	apps/system/style/window.css
	apps/system/test/unit/activity_window_factory_test.js
	apps/system/test/unit/activity_window_test.js
	apps/system/test/unit/app_window_manager_test.js
	apps/system/test/unit/app_window_test.js
	apps/system/test/unit/bootstrap_test.js
	apps/system/test/unit/cards_view_test.js
	apps/system/test/unit/mock_activity_window_manager.js