added the Channel.ModifyWith() to the registration FI
better Envelope.Clone.  Closes GH-171
can now use channel specific modifiers. Closes GH-165
moved the responsibility for serialization into the ChannelNode
envelope serializer takes in a ChannelNode
EnvelopeSerializer is smart enough to look for default serialization behavior per channel
can now set default serializers per channel. Closes GH-164