Add sticky area placeholder menu item
Merge branch 'master' into feature/sticky_items
Begin work on sticky items drag-and-drop
WIP on:

- Drag items to rubbish bin icon to remove
- Drag items to sticky area
Organisation of src files
Fixes #10 - Copy & paste in Nautilus doesn't work; stopped the current item
being re-copied every time the indicator gets refreshed (by polling mechanism)
Update README
Merge branch 'feature/sticky_items'