wip
enable pickling of enamldef classes
undo the custom save/restore hooks - just use pickle
save/restore the dock area and items using pickle
rename the custom enamldef unpickler function

these makes the unpickling compatible with pickle version 2.0, which
special cases unpickler functions named __newobj__
use the highest pickler protocol in the example
undo wip example changes
Merge pull request #143 from nucleic/feature-dock-area-save

Make enamldef objects pickable