This has been a big change, I'm now 3 days and a 3000 line diff in and I
finally got all the remote configuration settings converted to the new
up-front parsing.

Seems like quite a lot of work, since the only user-visible improvement is
these error messages:

	# git annex initremote demo type=directory directory=../foo encryption=none foo=bar
	initremote demo
	git-annex: Unexpected fields: foo
	
	# git annex initremote demo type=directory directory=../foo encryption=none exporttree=true
	initremote demo
	git-annex: Bad value for exporttree (expected yes or no)

But this involved paying down technical debt in a big code base, so of course it was
expensive.

Anyway, it should now be relatively easy to implement
`git annex initremote --list-params-for=S3`
