OMCI-lib-go: Relaxed MIB Upload Next response decoding

For OMCI, there are often amendments to G.988 that can introduce both new MEs as well as new Attributes to existing MEs. This presents a potential issue with the OpenONU code (operates as the OLT OMCI Stack) in receiving MIB UPLOAD NEXT responses with these changes.

The new MEs case is already handled in the code in case there are new ME's (or ones not supported) as well as vendor specific MEs.

For new attributes there is not.  The go-packet method of decoding does not easily allow for relaxed decode of protocols and a work around is required.  This issue will track this requirement.  

The first comment to this Jira outlines the first approach that may satisfy this requirement.