updated for new bind syntax
pep-8
added ScriptJobEvents

ScriptJobEvents are similar to events but they are scriptJob callbacks
rather than gui callbacks
better detection of objects which have not gone out of scope

The previous version used if self.c(): to check weakRef integrity; this
failed for objects with an oddball definition of __nonzero__ -
particularly instances of Control!  So, this version explicitly checks
for False or None.
added 'Deleted' callback two layout classes