merged current entity_management brach r3457-r3462. cleans up

merged current entity_management brach r3457-r3462.  cleans up
'_state' mamangement in attributes, moves __init__() instrumntation into attributes.py,
and reduces method call overhead by removing '_state' property.
future enhancements may include _state maintaining a weakref to the instance and a
strong ref to its __dict__ so that garbage-collected instances can get added to 'dirty',
when weak-referenced identity map is used.