Automatically remove old batch-edit datasets and recordsets.

[timo11]

[timo11]

BatchEdit datasets, and recordsets including changed records in secondary tables are saved after batch edits. There is already a process that runs at startup that deletes hidden uploader-generated recordsets that are more than a month old. We should make sure that works for b.e.-generated recordsets, and add something to remove old b.e-generated datasets.