Replace on_write with bus message

The current design of on_write is not very good as it depends on the view, the API is not linked to what kind of change happened etc.
I think we could have a general API that send a Bus message to the client which inform which records has been modified by his actions. The client could reload automatically the records already loaded (if they have not been modified).
There should be some kind of limit about the size of the message. For example if an action write on 20k records, it is better to just send to the client that any record of this type should be reloaded than sending the list of all ids.