Springer: Add Harvesting Logic

[Neodia]

The following harvesting logic should be added:

• Default harvesting :
  • Online files that are not present in S3 should be pulled from FTP.
• Config : Force Pull
  • When this flag is enabled, everything should be pulled from FTP even if the files exist in S3 already.
• Config : Filenames
  • When filenames are specified, the specific filenames should be reprocessed. This means that we are getting them from S3.
  • There will be also a configuration to specify that the files should be re-harvested from FTP aswell.

[drjova]

There will be also a configuration to specify that the files should be re-harvested from FTP aswell.

we could have a force flag in this case as well