Decoding of unsupported MEs by OMCI Library (go) is not supported

Currently, when an OMCI message with an unknown ME class ID is received, an error message is issued and the message decode fails.  This can break OMCI tasks such as a MIB Upload. The OMCI library should provide a mechanism to deliver this message to the library user (OpenONU golang Adapter in this case) and allow it to process it further.

The decode process should successfully decode the response/notification with the unknown ME class wrapped properly by a ManagedEntity and ManagedEntityDefinition structs that the library user can use for further processing

In the ManagedEntity struct, the attribute value map will contain the unknown attributes as a single byte array if the received attribute mask is non-zero.  

In the ManagedEntityDefinition struct:

• The Name field should contain textual information indicating that this is an unknown class ID.
• The Support field enumeration should be expanded to include an enumeration for UnsupportedManagedEntity (for class IDs that are G.988 standard values) or UnsupportedVenderSpecificManagedEntity (for the range of Vendor Specific Class IDs)

Note: The ManagedEntityDefinition provided will only exist in the context of the message.  Meaning that if given only a Class ID and you ask the library to look up the ME Definition, it will return that the Class ID was not found.

For additional information, see VOL-3532 for a discussion of the original issue.