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.
Merge pull request #627 from 4teamwork/pg_xxs_fixes

Security fixes: avoid injecting javascript (XSS) using safe_html transforms.