Corrected one-way MEP proposal

Somewhere along the line, one or more processors put gibberish into the
href of anything that looked like a link.  I've fixed that here.  I've
also edited the state machine descriptions, which still had a little bit
of cut-n-paste left over from the request-response MEP description I
started from.  These descriptions now are deliberately /too/ minimal
(probably), but the state machines themselves may not be.