Separate crawling from processing/indexing
- no more OAI PMH processing service
- fetch files depending on interface
- then iterate files
(from redmine: issue id 594, created on 2018-01-22tgradl, closed on 2018-01-24)
(from redmine: issue id 594, created on 2018-01-22tgradl, closed on 2018-01-24)