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.

Command/Log.hs

@@ -148,7 +148,11 @@ getLog key os = do
 	config <- Annex.getGitConfig
 	let logfile = p </> locationLogFile config key
 	inRepo $ pipeNullSplitZombie $
-		[ Params "log -z --pretty=format:%ct --raw --abbrev=40"
+		[ Param "log"
+		, Param "-z"
+		, Param "--pretty=format:%ct"
+		, Param "-raw"
+		, Param "--abbrev=40"
 		, Param "--remove-empty"
 		] ++ os ++
 		[ Param $ Git.fromRef Annex.Branch.fullname