GrantleeHeaderFormatter: Move list and date formatter into grantlee.

Summary:
With this we have a more clean interface, what we can do with
AddressLists and Dates and to not blown the namespace.

Currently I'm very unhappy with the code duplication for Mailboxes and
QShardPointer. Maybe someone can help me to improve this.

Reviewers: vkrause, mlaurent

Subscribers: kde-pim

Tags: #kde_pim

Differential Revision: https://phabricator.kde.org/D13039