Add bookmark folders as context menu
Localize user string in the javascript code
Make "command" method only applies to menuitem

This commit fix the bug that covering the "scroll button" triggers
the "command" event.
Make sure our destination is a bookmark folder
Try the parent document if no stringBundle found

Bookmarks side panel has no stringbundleset defined, so the parent
docment has to be quried.
Add screenshots for version 0.1