wip RawFilePath 2x git-annex find speedup

Finally builds (oh the agoncy of making it build), but still very
unmergable, only Command.Find is included and lots of stuff is badly
hacked to make it compile.

Benchmarking vs master, this git-annex find is significantly faster!
Specifically:

	num files	old	new	speedup
	48500		4.77	3.73	28%
	12500		1.36	1.02	66%
	20		0.075	0.074	0% (so startup time is unchanged)

That's without really finishing the optimization. Things still to do:

* Eliminate all the fromRawFilePath, toRawFilePath, encodeBS,
  decodeBS conversions.
* Use versions of IO actions like getFileStatus that take a RawFilePath.
* Eliminate some Data.ByteString.Lazy.toStrict, which is a slow copy.
* Use ByteString for parsing git config to speed up startup.

It's likely several of those will speed up git-annex find further.
And other commands will certianly benefit even more.

Annex/MetaData.hs

@@ -37,7 +37,7 @@ import Data.Time.Clock.POSIX
  -
  - Also, can generate new metadata, if configured to do so.
  -}
-genMetaData :: Key -> FilePath -> FileStatus -> Annex ()
+genMetaData :: Key -> RawFilePath -> FileStatus -> Annex ()
 genMetaData key file status = do
 	catKeyFileHEAD file >>= \case
 		Nothing -> noop
@@ -53,8 +53,8 @@ genMetaData key file status = do
   where
 	mtime = posixSecondsToUTCTime $ realToFrac $ modificationTime status
 	warncopied = warning $ 
-		"Copied metadata from old version of " ++ file ++ " to new version. " ++ 
-		"If you don't want this copied metadata, run: git annex metadata --remove-all " ++ file
+		"Copied metadata from old version of " ++ fromRawFilePath file ++ " to new version. " ++ 
+		"If you don't want this copied metadata, run: git annex metadata --remove-all " ++ fromRawFilePath file
 	-- If the only fields copied were date metadata, and they'll
 	-- be overwritten with the current mtime, no need to warn about
 	-- copying.