Misc todo

[simontaylor81]

• [ ] Clear previous script when loading new project
• [x] Open documents when adding to project
• [x] Add multiple files to project at once
• [ ] Save changes prompt when closing document
• [x] Clear output window when re-running script
• [x] Proper output from script tests
• [ ] Remove items from recently opened list if they don't exist
• [ ] Save window layout
• [ ] Save open documents outside of project file
• [ ] Make open document set a service to avoid slightly tangled dependencies?