Implement a centralized Exporter

[Thomas-Gelf]

Export logic is distributed over existing objects, which renders export (baskets) hard to troubleshoot. First step: create a dedicated Exporter, collect all special cases in one place.

[Thomas-Gelf]

Tested with various objects, export is the same apart from the following differences:

• originalId is no longer exported, it has shown to not be useful at all
• all exported properties are now sorted, formerly some have not been
• empty Job settings are now an empty dictionary (and not an array, which was technically not correct)