Bulk data transfers between datasets

[goldpbear]

The Django admin panel lets us move individual places from one dataset to another, but there is no way to select a set of places and move them all in bulk.

Bulk data transfer would be a great feature to have, though, especially as we develop flavors with numerous datasets.

Ideally, bulk data transfer would be an option listed in the dropdown menu in the Places section of the Django admin panel. Users would select the places they want to move, select the bulk transfer option, then select the destination dataset from a list.