addunused, dropunused: Support --json and --json-error-messages

This also changes addunused to display the names of the files that it adds.
That seems like a general usability improvement, and not displaying the input
number does not seem likely to be a problem to a user, since the filename
is based on the key. Displaying the filename was necessary to get it and the key
included in the json.

dropunused does not include the key in the json. It would be possible to
add, but would need more changes. And I doubt that dropunused --json
would be used in a situation where a program cared which keys were
dropped. Note that drop --unused does have the key in its json, so such
a program could just use it. Or could just dropkey --batch with the
specific keys it wants to drop if it cares about specific keys.

Sponsored-By: the NIH-funded NICEMAN (ReproNim TR&D3) project

Command/Unused.hs

@@ -322,12 +322,12 @@ unusedSpec m spec
 
 {- Seek action for unused content. Finds the number in the maps, and
  - calls one of 3 actions, depending on the type of unused file. -}
-startUnused :: String
-	-> (Key -> CommandPerform)
-	-> (Key -> CommandPerform) 
-	-> (Key -> CommandPerform)
+startUnused
+	:: (Int -> Key -> CommandStart)
+	-> (Int -> Key -> CommandStart) 
+	-> (Int -> Key -> CommandStart)
 	-> UnusedMaps -> Int -> CommandStart
-startUnused message unused badunused tmpunused maps n = search
+startUnused unused badunused tmpunused maps n = search
 	[ (unusedMap maps, unused)
 	, (unusedBadMap maps, badunused)
 	, (unusedTmpMap maps, tmpunused)
@@ -337,7 +337,4 @@ startUnused message unused badunused tmpunused maps n = search
 	search ((m, a):rest) =
 		case M.lookup n m of
 			Nothing -> search rest
-			Just key -> starting message
-				(ActionItemOther $ Just $ UnquotedString $ show n)
-				(SeekInput [])
-				(a key)
+			Just key -> a n key