Rename transcoder to Transcoder to reflect proper c# naming conventions

Change-Id: I7c96ce79eab204f22ed28a7f9616308cfcc845ab
Reviewed-on: http://review.couchbase.org/42820
Reviewed-by: Simon Baslé <simon@couchbase.com>
Reviewed-by: Jeffry Morris <jeffrymorris@gmail.com>
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>