Cosmetic changes in Table::Relator
[importer] Implement SourceFile
[importer] Refactor Downloader to use SourceFile
[importer] Refactor params order in Ogr2ogr
[importer] Loader now takes a Job and a SourceFile
[importer] Refactor job to not store file details
[importer] Refactor runner to use a job and a downloader as collaborators
[importer] Adapt acceptace specs to latest changes
[importer] Remove Candidate