Bulk edit affiliations of people

This feature request is the ability to apply some changes (delete an affiliation, add a new one) to the result of a query (like all the people affiliated to company X).

The issue names no files, tests, or entry points. Start by locating the code that queries people and applies affiliation changes; done means supporting deletion or addition of an affiliation across everyone returned by a query such as people affiliated with company X.

Written by the indexing model from the issue text.