Added a "uid" field to Layout so that Alfred can learn frequently used options.

If you wish Alfred to learn frequently used items, you need to set the "uid" attribute of the item node to something uniquely identifiable, so that Alfred will show frequently selected items to the top of the list. Added a "uid" field to the Layout class for this.
Minor cleanup
Merge pull request #1 from BenziAhamed/patch-1

Added a "uid" field to Layout so Alfred can learn frequently used options