Allow staff to change applicant/author of an application

[frjo]

A new person in an organisation is taking over the application. The applicant has multiple accounts. There are a number of scenarios where this would be handy.

A select/search field that list all current applicants and a confirmation step.

We could add this to the standard edit view or create a specific modal for just changing applicant/author.

The later might be best since staff do not always have edit perms on applications.