Merged Andy's new "set_project_modified" code, which improves OpenShot's ability to prompt users to save projects when exiting, and disables the save button when there are no changes to save.
I had to extend this method to incorporate the "refresh xml" flag which I had used previously to determine when the XML needed to be re-generated.
The final method signature now looks like: set_project_modified(is_modified=False, refresh_xml=False)
Removed right click menu for our transitions tree... which was left over code from the file tree.
New Project screen now defaults to the "Desktop" correctly when creating a new project.