Regrep revised design principles

Here is my revision of the Design Principles - revisions consisted
mostly of deleting points we agreed to delete in Paris (and the
mention of X3.285 and XML Schema at the top).  The point about 
assuming the use of HTTP may need clarification; I have still to
write up a short piece on THTTP, but the point is really that
unless we agree to a single protocol we have to specify things
at a higher level, which is a bore.

regards, Terry