BF: smooth out a couple wx-3.0 issues

- mac only (?): hack to pop up a gui has the side-effect that you can open and switch among wx windows
- PySimpleApp was deprecated in wx 2.9+, update to wx.App(False) as needed

- locally: get quite a few unrelated visual errors (avbin, refresh rate, ...) when run the test-suite but none on travis-ci