convert TopFilePath to use RawFilePath

Adds a dependency on filepath-bytestring, an as yet unreleased fork of
filepath that operates on RawFilePath.

Git.Repo also changed to use RawFilePath for the path to the repo.

This does eliminate some RawFilePath -> FilePath -> RawFilePath
conversions. And filepath-bytestring's </> is probably faster.
But I don't expect a major performance improvement from this.
This is mostly groundwork for making Annex.Location use RawFilePath,
which will allow for a conversion-free pipleline.

Assistant/WebApp/Configurators/Delete.hs

@@ -78,7 +78,7 @@ deleteCurrentRepository = dangerPage $ do
 			sanityVerifierAForm $ SanityVerifier magicphrase
 	case result of
 		FormSuccess _ -> liftH $ do
-			dir <- liftAnnex $ fromRepo Git.repoPath
+			dir <- liftAnnex $ fromRawFilePath <$> fromRepo Git.repoPath
 			liftIO $ removeAutoStartFile dir
 
 			{- Disable syncing to this repository, and all