well along the way to fully quiet --quiet

Came up with a generic way to filter out progress messages while keeping
errors, for commands that use stderr for both.

--json mode will disable command outputs too.

Remote/Helper/Ssh.hs

@@ -106,8 +106,8 @@ rsyncHelper m params = do
 	a <- case m of
 		Nothing -> return $ rsync params
 		Just meter -> do
-			h <- mkProgressHandler meter
-			return $ rsyncProgress h params
+			oh <- mkOutputHandler
+			return $ rsyncProgress oh meter params
 	ifM (liftIO a)
 		( return True
 		, do