Quick search: allow to display the birth date in the search results

Add UI allowing administrators to configure additional options for quicksearch results (e.g. Birth Date or other values).
Instead of cherry-picking what options get to go in the search admin UI (I would add most of those that Kurund mentioned, but I understand that it could lead to a cluttered and hard to use admin UI).

• in search admin (/civicrm/admin/setting/search?reset=1), add a link to optionValue config?
• in optionValue?action=add, if it's the contact_autocomplete_options or contactref group, have a dropdown widget on the "value" field? – CRM/Admin/Form/OptionValue.php already has some "gName"-specific handling.

— original post —
Add an option to the search settings so that the quicksearch results may display the birth date of individuals.

My users find this useful to distinguish duplicates (the phone number is not reliable enough).