fs/p9p/new: various client and server cleanup Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: add documentation comment for package Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: cleanup encoding/decoding We take some time to cleanup the codec implementation. The need for the message to implement the Message interface has been removed to allow flexibility in what can land in the message field. Error types can be returned directly now. The messages have been moved into a separate file. We also ensure that the number of pointer types is reduced in deserialized messages, hopefully avoiding unnecessary pointer traversal. Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: add version to context Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: refactor to use interface for channel Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: correct message encoding for Rerror message Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: proxy end to end fully working Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: initial implementation of 9ps To begin testing the server implementation, we defined a 9ps cmd. This simply proxies a client connection to a running ufs server but should let us develop a prototype without implementing all of ufs. Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: fix cat command in 9pr Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: allow 9pr configurable by flags Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: stat implementation and correct dir/Rstat encoding Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: remove unused tagsPool implementation Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: fully working ls with ufs The repl and client session work fully with rminnich/go9p/ufs. The key to this was proper support for directory serialization, which is subtle. The size field for Rread was the incorrect size. Several robustness improvements are also included. Issues with the timeouts and missing error returns have been addressed. Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: refactor channel framing After a few connection bugs and framing issues, the transport has been refactored into a channel that manages raw message sending. More importantly, this frees up pre-session protocol version negotiation. To support this, the encoder and decoder have been folded into a Codec interface. The encoding support still needs work, but this has made the server and client code much simpler to understand. Signed-off-by: Stephen J Day <stephen.day@docker.com>

fs/p9p/new: ls and cat command now fully working Signed-off-by: Stephen J Day <stephen.day@docker.com>