Improve stability and add shortcut key.

Achieve 2-way sync with Chrome's built bookmark. Now if bookmark is removed by Chrome's default bookmark functionality, LightMaker is aware and update its icon correctly.

Add shortcut key:

1. Ctrl+D or Cmd+D to add bookmark, now will replace default bookmark popup.
2. When popup is on, press Ctrl+D or Cmd+D again to save scrollbar position.