add VerifiedCopy data type

There should be no behavior changes in this commit, it just adds a more
expressive data type and adjusts code that had been passing around a [UUID]
or sometimes a Maybe Remote to instead use [VerifiedCopy].

Although, since some functions were taking two different [UUID] lists,
there's some potential for me to have gotten it horribly wrong.

Command/Sync.hs

@@ -460,8 +460,8 @@ syncFile ebloom rs af k = do
 		-- includeCommandAction for drops,
 		-- because a failure to drop does not mean
 		-- the sync failed.
-		handleDropsFrom locs' rs "unwanted" True k af
-			Nothing callCommandAction
+		handleDropsFrom locs' rs "unwanted" True k af []
+			callCommandAction
 	
 	return (got || not (null putrs))
   where