Bugfix: Disable label close, Shutdown cleaning, TabView in new window

This commit is a bit ugly, it has many changes.
Changed var window -> aWindow, reorganized code, added new emcInit check
with browser delay status.

Haven't fixed issues with firefox v20-23 which have a bug with
instanceof window.HTMLElement. It probably won't be fixed as they are
old releases.
bugfix toogleBookmarksSidebar typo, removed toggleDownloadsSidebar

Downloads sidebar has been deprecated due to new download manager
forced delay for ff23
ready for release 0.4.1
added updateTabsVisibilityStatus to tabs popupmenu

there in the popupmenu there is now an indicator which tabs
are visible just like in the firefox "Show All Tabs" button menu
removed inline styling, added loadAndRegisterSheet
small fixed and comments/samples for future
always show visible tabs indicator on tabsGroupsMenu
ready to release 0.4.2