REST API: Replicator getFilesMetadata

Change-Id: I8b1fcd177c13c42043c3560890dd22114ce171a5
Reviewed-on: http://naan.mimuw.edu.pl:8001/120
Tested-by: Nebulostore Nebulostore <nebulostore@gmail.com>
Reviewed-by: Bolek Kulbabinski <bkulbabinski@gmail.com>