AppLauncher: divide constants for strings and UI items
AppLauncher: improve ||
AppLauncher: validate main popup showing
AppLauncher: change setting for link extensions
AppLauncher: rewrite functions for document checks
AppLauncher: add to commit: 9c96acb
AppLauncher: fx18: |nsIWebBrowserPersist::saveURI| gained a new argument

* see https://bugzilla.mozilla.org/show_bug.cgi?id=794602
* see https://developer.mozilla.org/en/docs/Updating_addons_broken_by_private_browsing_changes
AppLauncher: use |nsIPromptService|
AppLauncher: sift applications
AppLauncher: change warning strings
AppLauncher: minor cleanup

* No major changes
* update comments
* arrange formattings: add braces, add new-lines, optimize temporary local
  variables