Move project templates (=folders) into Project menu

[humdingerb]

It'd be more consistent if the "File" menu only had actual files as "New" templates (plus the generic "New folder"). These new files always get added in the project that was selected when "New" was invoked.

When the user wants to start a new project, it'd be intuitive to look into the "Project" menu.

This would also help cut down on the entries in each menu and emphasizes the distinction "new file <-> new project".