treeIterator added to walk any subtree if a treectrl.
__iter__ removed from expander.
DirectoryExpanderPopup.onPanoramaConfig is temp test method of
treeIterator implementation.
1. generator execution capability added to expanders. It enables the
execution of an operation recursively on a subtree. ExpanderPopup object
calls with the generator to enable menu activation.
2. AEBChecker bug testing and fix added: it checks the
'Exif.Photo.ExposureMode' value to make sure the photos are in a bracket
series
3. A new checker called SameCameraChecker is added. Series taken at the
same time with 2 different cameras are mixed without this.