Make it possible to paste nodes when a list cursor is active.
Show prompt when right clicking on an item or anywhere on the scene
Simplify delegating clicks to the sceneHandlerItem

- The item is now always under the mouse cursor when clicking.
Make the command prompt adjust its position when re-showing
Make the position and region of Cursors use owner local coordinates
Move model and concurrency classes in new subdirectories
Introduce a ModelManager class that handles all existing Models
Clean up code associated with the prompt.
Introduce an abstract command for creating named objects with attributes
Rename some command classes
Add a create project command to the default scene handler
Fix cursor behavior when creating new project and other small issues

- Scene now exposes the top level items
- SetCursorEvent now can also search for all items in the scene
- CommandPrompt now has its own Z level
Fix the category of AutoComplete visuals to be that of command items
Automatically show the prompt at startup

- For some reason the selection of the text is not visible. Needs to be
fixed.
Remove a useless update call
Fix some issues with showing the prompt at the beginning.
Add a model and visualization for a throw expression
Make the amount optional for new expression and fix the inferred type
Add interaction support for the new expression for single objects
Add interactions for "throw"