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/Edit.hs

@@ -238,7 +238,7 @@ checkAssociatedDirectory cfg (Just r) = do
 		RepoGroupStandard gr -> case associatedDirectory repoconfig gr of
 			Just d -> inRepo $ \g ->
 				createDirectoryIfMissing True $
-					Git.repoPath g </> d
+					fromRawFilePath (Git.repoPath g) </> d
 			Nothing -> noop
 		_ -> noop