go(): pass echo_server as channel constructor

msg_channel_open(): construct a new channel class & send confirm

send_channel_request_failure(): new method
Remote_Channel.__init__(): probably incorrect attempt to increment channel id

undo accidental renaming of transport->ssh_transport
server side authentication: Authenticator and Public_Key_Authenticator classes

msg_newkeys(): call send_newkeys() *before* setting them

_connect(): undo accidental s2c/c2s swaps: (ehuss)

get_private_key_blob(): get private, not public vals
create(): initialize a fresh key (unused as of yet)

msg_kexdh_init(): calculate correct value for for f