Move `Person.is_active` from person form to permissions form
Move `Person.is_active` from person form to permissions form

`is_active` field is mostly admin-related field, because it allows users
to log into the site.  It should be under admin-only form, and
permissions form fits it quite right.

vahtras/amy,pbanaszkiewicz/amy,swcarpentry/amy,swcarpentry/amy,vahtras/amy,swcarpentry/amy,pbanaszkiewicz/amy,vahtras/amy,pbanaszkiewicz/amy