scratch20: Fix custom blocks
Move broken old tests into temporary directory.
Support pickle with kurt objects.

Added testing to verify simple projects can be pickled.

Note: At this time only pickle.HIGHEST_PROTOCOL is supported. To support older
protocols, all classes that define __getattr__ or __slots__ need to be updated
to include __getdata__ and __setdata__. This requires changes or monkeypatches
to construct.
Fix and verify that pickle files can be loaded.

__getattr__ should call its parent's __getattr__ method when appropriate.
fromstring and tostring are depricated in pillow >= 2.0.
Fix obscure Scratch 2.0 image loading bug
Significantly faster Scratch 1.4 image loading
Merge branch 'bboe/pickle_support'