Extend transition guards with agency-checks for the some forwarding transitions:

The following transitions should also be available, as agency transition,
when the user is a agency member of the assigned org_unit.

* forwarding-transition-assign-to-dossier'
* forwarding-transition-reassign'
* forwarding-transition-close'
* forwarding-transition-reassign-refused'
Merge pull request #626 from 4teamwork/pg_forwarding_agency_condition

Extend transition guards with agency-checks for some forwarding transitions:
Assign to Dossier: use Yearfolderstorer instead of manually moving the forwarding to the yearfolder.
Admin_unit intern `remote_requests` uses now unrestricted traversing.

It's not be secured that all parts from the traversing path,
are available for the user. But because the remote request is only used from other
intern functions, it makes sense to use `unrestrictedTraverse`.
Merge pull request #625 from 4teamwork/pg_assign_to_dossier_fix

Assign to dossier fix
Dossier overview: Use html-safe transforms in task link generation.

To avoid injecting javascript etc. (XSS), with the task title.
Task overview: only render attributes with the `structure` command, which contains generated html.

To avoid injecting javascript etc. (XSS), with the task or dossier title.
Made Task.get_link generation XSS-save using the safe-html transform.
Task actionmenu: drop useless structure command when display submenu title.
Made Actor.get_link generation XSS-save using the safe-html transform.
Mail attachment extraction: Made download link generation XSS-save using the safe-html transform.
Made Mail preview tab XSS-save using the safe-html transform for the mail-body display.