Websocket protocol enhancement collection

[Apollon77]

Collection and idea list for websocket enhancements for a protocol update:

• return more details errors on commissioning issues
• return "device data updated" websocket message to update a "device last seen" timestamp (also see Add a diagnostic timestamp for the last communication received from the node #308)
• return attributes updates that were received together for one cluster in one message (same dataversion)
• query data about product for commissioning
• make websocket data consistent (see IDs vs names for struct fields #492)
• reconsider timestamps (see use html <time> element #154)
• ...