parser should emit error on protocol errors

[seriousme]

As requested in: moscajs/aedes#1042

MQTT packet currently accepts:

1. connect packet with protocolVersion 3 (3.1) and no clientId
2. connect packet with protocolVersion 4 (3.1.1) no clientid and clean=false
3. connect packet with protocolName that does not match protocolVersion (e.g. protocolName "MQTT" for protocolVersion 3 and "MQdisp" for protocolVersion 4 and 5

All 3 are considered protocol errors in the MQTT standard.

Kind regards,
Hans

[robertsLando]

cc @mcollina