Fixed use of URN (vs URI)

- actual hrefs in documents and commands don't have protocol
  or endpoint
- correct usage is 'URN' not 'URI'
Removed 400 Bad Request for GET
Added Date-Modified and ETag for PUT success

- when a resource is modified, the date and ETag must change
- it's better to return these explicitly after a successful PUT
First draft of RFC

- specified grammar for the protocol
- specified interconnection (socket) model
RFC 2 and RFC 4 moved to draft state

- reference implementation now working, at UnifyProject/xrap