remove Params constructor from Utility.SafeCommand

This removes a bit of complexity, and should make things faster
(avoids tokenizing Params string), and probably involve less garbage
collection.

In a few places, it was useful to use Params to avoid needing a list,
but that is easily avoided.

Problems noticed while doing this conversion:

	* Some uses of Params "oneword" which was entirely unnecessary
	  overhead.
	* A few places that built up a list of parameters with ++
	  and then used Params to split it!

Test suite passes.

Assistant/WebApp/Gpg.hs

@@ -69,7 +69,11 @@ getGCryptRemoteName :: UUID -> String -> Annex RemoteName
 getGCryptRemoteName u repoloc = do
 	tmpremote <- uniqueRemoteName "tmpgcryptremote" 0 <$> gitRepo
 	void $ inRepo $ Git.Command.runBool
-		[Params "remote add", Param tmpremote, Param $ Git.GCrypt.urlPrefix ++ repoloc]
+		[ Param "remote"
+		, Param "add"
+		, Param tmpremote
+		, Param $ Git.GCrypt.urlPrefix ++ repoloc
+		]
 	mname <- ifM (inRepo $ Git.Command.runBool [Param "fetch", Param tmpremote])
 		( do
 			void Annex.Branch.forceUpdate