0.5 draft of new dumnfile docs

Thanks to Steve Butler for clearing up one of the open questions. I've
added another. The current list is:

1. In the Credits section I note that portions of this document are
derived from notes by Ben Sussman, and mention the people who have
helpfully answered questions. I would also like to credit the
original designers of the format (at least one of whom must have been
Greg Stein) and attach a date to the original design discussion. Can
someone fill me in on the history?

2. Does a copy operation carry with it properties? In particular,
if I do a replace on a file without the svn:executable property
from a copy source with the svn:executable property, what happens?

-- 
		Eric S. Raymond