Rename isDbjsObject to isDbjsKind

It's about all type of dbjs wrappers, descriptors, multiple items,
objects. so `isObject` is misleading
Fix error message in validDbjsKind
`isDbjsObject` and `validDbjsObject`
Fix typo in _getMultipleItem_
objectSnapshot utility
Rely on last *own* event
Improve events handling
`extensions` live property for types
Do not self destroy nested objects
Fix has and hasOwn for nested and multiples
Fix size for nested/multiple by proto
Fix iteration for nested/multiple by proto
Unserialize value first
Update up to changes in es6-set
Fix iteration over constant sets
Fix enumerability for newly created nested