use |getIcon| API to get tab icon URL

* fx22: use it to avoid leaking the -moz-resolution media fragment
  see https://bugzilla.mozilla.org/show_bug.cgi?id=828508
* cf. commit: be458ab
fx21: remove icon of groups menu in all tabs popup

* |alltabs.png| has been deleted and I can't find a good built-in icon for the
  menu
  see https://bugzilla.mozilla.org/show_bug.cgi?id=670684
refactor making menu items

* rename |kBundle| to |kUI|
improve setting user preset

* use special replacement patterns |$n| to make a new URL
* support a linked image URL as a source URL
* add |disabled| key to disable a item temporarily