BF: smooth out a couple wx-3.0 issue

- 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+

- get quite a few visual errors when run the test-suite (avbin, refresh rate, ...), will commit anyway
TEST: autoLog=False in test_projections / Test_class_WindowWarp
FF: ensure we have a wx.App prior to showing a dialog in gui.py

- make a temp one if needed, retain a global reference to it
DOC: add icon to "about" page if wx-3.0
FF: wx-3 - small icons work but look bad on mac
RF: remove dump_namespace from Builder

- no longer needed, hopefully (was useful for debugging)
Merge pull request #663 from jeremygray/master

BF: smooth out a couple wx-3.0 issues