CONNACK return code references are inconsistent

The WD04 spec contains inconsistent references to CONNACK return codes

Line 537 uses a HEX reference to a return code "CONNACK with return code 0x01"
Lines 678 and 754 refer to "return code 2" (from the table on line 752) and repeat the meaning "Identifier Rejected"

I think there is value to keeping the enumerated table for reference (reserving 6-255), although I can't see reference to the other return codes listed

The spec should use consistent terminology for referencing return codes