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.

Command/Unlock.hs

@@ -57,5 +57,5 @@ perform dest key = do
 cleanup ::  RawFilePath -> Key -> Maybe FileMode -> CommandCleanup
 cleanup dest key destmode = do
 	stagePointerFile dest destmode =<< hashPointerFile key
-	Database.Keys.addAssociatedFile key =<< inRepo (toTopFilePath (fromRawFilePath dest))
+	Database.Keys.addAssociatedFile key =<< inRepo (toTopFilePath dest)
 	return True