settings.read returns any specified default value even if there is no
GUI.

settings).

actions.__init__ module contains aliases for all the global Action
classes. FSLEyesFrame no longer stores a dict of {AuiPaneInfo :
ViewPanel} mappings, because AuiPaneInfo objects are evidently not
persistent, so I cannot use them as dict keys. New action -
ClearPerspectiveAction, which delets all user-saved
perspectives. SavePerspectiveAction is functional.  Perspectives module
is functional, but needs more work w.r.t. managing built-in
perspectives.

starting with the fsl.utils package.

not.

 - All GLObjects test to see if opts instances have a parent, before
   doing things with their sync properties.
 - Render.py bug - using fsl/utils/layout functions, passing
   showLabels=True, but then passing no labels. Renderpy usage fixed,
   and layout test added (reverts to showLabels=False if no labels are
   provided)
 - CanvasPanel screenshot was passing all overlays, instead of just
   enabled/saved ones
 - settingspy imports wx inside functions, in case we're running in
   headless mode
 - In my SliceCanvas.genGLObject refactoring, I removed a critical piece
   of functionality - genGLObject(updateRenderTextures=True) was not
   updating render textures.

module, just in case I decide to use a different approach to settings
persistence. Overlay module saves the last used directory as a setting,
and does it properly, unlike before.