Stringify incoming group ids

Otherwise when we try to make their local storage keys they look like:
"egroupByteBuffer(offset=4,markedOffset=-1,length=28,capacity=112)"
Group ids are stored in groupId
Group ids should be converted to ArrayBuffers for transport
Store group ids as strings
If for some reason a group has no name, provide a default
Put groupid back in id field also
Quickfix for wonky tagsinput