Allow hour tracking for non-users

[flack]

Reported by flack on 14 Mar 1914 23:36 UTC
There are situations where it's necessary to manage hour reports of people that don't have accounts (f.x. editing reports of users with temporary accounts that have expired), so there should be another way to make person objects eligible for hour reporting.

Unfortunately, we can't use ACLs, because that would require valid accounts as well, maybe a membership to a special group (or to owner_organization) would be the best solution (if chooser/autocomplete can be made to understand this).

Migrated-From: http://trac.openpsa2.org/ticket/162