#503 UNDO after open deletes Project contents

[mattk-sfn]

2.0 RC1

Start GP
Open a Project
*Press "Undo"

-> The whole project is deleted.

Expected behavior:

Opening a file is not an undoable operation.
"Undo" should not do anything until the first actual
command has been completed.
Multiple undos should not go back beyond the original
file contents.