[GREENFOOT-713] An empty stage changes its location and size if a new scenario is opened.
The correct behaviour for different cases as agreed:
In case of a new window opened for this scenario: all properties should be loaded from the project's properties file, if they available.
In case of existing empty window: location of the window shouldn't change; the width/height should only get bigger if the value from the properties bigger than the current one.
- Issue type: Task
- Priority: Medium