define function as property in object
count items instead of confusing flag
update settings for my PC environment
tidy up codes for disused AllTabs.uc.js

* move |customizeTabTooltip()| to Misc.uc.js as the general function
* remove related CSS
fx30: remove comment for fx30

* it is not suitable to use |Task.async| here
  @see https://bugzilla.mozilla.org/show_bug.cgi?id=966182
handle exception for getting closed tabs/windows

* the exception is not thrown for windows but I match a form with the function
  for tabs for future changes
  see http://mxr.mozilla.org/mozilla-release/source/browser/components/sessionstore/src/SessionStore.jsm#1601
* it seems that errors of sessionstore at startup often occur in Fx30 on my
  environment