Added initial protocol documentation.

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+Next File Transfer Protocol
+===========================
+
+Introduction
+------------
+
+Next File Transfer uses a simple protocol where a single character defines
+a message type. 
+
+The following are standard compents of a message:
+
+> <NNNNN>	5 ASCII digits making up a zero-padded number.
+> <N bytes>	A stream of N bytes.
+
+
+Put File
+--------
+
+The format of the message from the client is:
+
+> A		Put file command
+> <NNNNN>	Length of filename
+> <N bytes>	The filename
+> <NNNNN>	Length of the data for the file.
+> <N bytes>	The data.
+
+The server responds with either:
+
+> OK		The command completed OK
+
+or:
+
+> !E		There was an error writing the file.
+
+
+Get File
+--------
+
+The format of the message from the client is:
+
+> B		Put file command
+> <NNNNN>	Length of filename
+> <N bytes>	The filename
+
+The server responds with either:
+
+> OK		The command completed OK.  The file contents will follow.
+> <NNNNN>	The length of the following data.
+> <N bytes>	The data frin from the file.
+
+or:
+
+> !E		There was an error reading the file.
+
+
+Change Directory
+----------------
+
+The format of the message from the client is:
+
+> C		Change directory command
+> NNNNN		Length of pathname
+> <N bytes>	The pathname
+
+The server responds with either:
+
+> OK		The command completed OK
+
+or:
+
+> !E		There was an error changing to the directory
+
+
+Create Directory
+----------------
+
+The format of the message from the client is:
+
+> D		Create directory command
+> NNNNN		Length of pathname
+> <N bytes>	The pathname
+
+The server responds with either:
+
+> OK		The command completed OK
+
+or:
+
+> !E		There was an error creating the directory