Fix for Issue #1651

Add ability to look up a word in dictionary from the "Edit Note" dialog.
![screenshot_2014-03-17](https://f.cloud.github.com/assets/3719196/2443090/f1827dde-ae2d-11e3-8629-3169d4cba624.png)

I've put the menu item at the end. Please let me know if you want me to change this.