Fix handling of setItems in fragment
`delete` methods, that do deep deletion of object
String normalization
Handle reverse only for object type item values
Signal remove logic should also fire events
Emit update only if obj was evented
Adjust listeners for possible null events
Simpler logic for repeated events
Deletion of item should delete all it's relations
Remove all item's relations on batch delete
Fix bug related to validation of deep relations
Add writeOnce to meta property names list
Item values should added only in special cases