Open Tailor projects on MacOS opens empty window

[davidfokkema]

If Tailor is not yet open, if you double-click on the a Tailor project on the desktop or in the Finder, it opens an empty Tailor window. This is probably because the 'open event' is sent to the splash screen instead of to the application proper. Extend the splash screen to accept those events or maybe just instantiate the main app in __main__.py instead of instantiating a default QApplication.