We have a CSV import for datasets, and export (AB-386), but this functionality only considers the classes and items of a dataset. It doesn't include the dataset description or descriptions of any class if they're set.
We should include this information in the CSV file that we export, and support reading it during a dataset import. We could include the data as specially named fields in the csv:

description, a dataset description
description:class1, "a description for class1"
description:class2, another description for class2

These fields should be exported at the beginning of the file, but could be present on any line when being imported.