--Developer notes--

1) About the copied modules

Some utility modules are copied into all 4 gadget subfolders.
This is a bit tedious, but the subfolders are used to produce
standalone executables; a common/shared folder can be painful 
to manage in that context (see PyEdit nested in PyMailGUI);
and symlinks don't work evenly across all PyGadgets platforms. 

2) PyPhoto's viewer_thumbs.py change detection merits redesign

See this file for this caveat: by copying file modtimes to 
thumbnail images, it defeats timestamp-based backup programs
like Mergeall, and requires all copies to be manually deleted
if thumbnail size changes.  A separate record of modtimes 
would fare much better, but thumbnail sizes cannot be changed
by users, and the project ran out of time for changes.

  UPDATE => this was addressed in PyPhoto 2.1 (in PyGadgets 4.2)
  by storing thumbnail images, and their source-image dates, in 
  a single pickle file per folder.  This also reduces the number
  of files added by PyPhoto, and uses similar time/space.

3) viewer_thumbs.py is probably forever forked

The viewer_thumbs.py file takes different forms in PyPhoto and
thumbspage, but they now differ too much to reconcile and reuse.