split off versionedExport from appendonly

S3 uses versionedExport, while GitLFS uses appendonly.

This is groundwork for later changes.

Remote/Rsync.hs

@@ -101,6 +101,7 @@ gen r u rc gc rs = do
 				{ storeExport = storeExportM o
 				, retrieveExport = retrieveExportM o
 				, removeExport = removeExportM o
+				, versionedExport = False
 				, checkPresentExport = checkPresentExportM o
 				, removeExportDirectory = Just (removeExportDirectoryM o)
 				, renameExport = renameExportM o