Add --view option to open contact

Summary:
Opens KAddressbook and selects the contact or contact group
matching the given Akonadi URL. Also introduces kaddresbook-view
desktop file to allow opening the URL through a desktop service.

Test Plan: kaddressbook --view "akonadi://?item=<some-contact-akonadi-id>"

Reviewers: KDE PIM, winterz

Reviewed By: KDE PIM, winterz

Subscribers: winterz, kde-pim

Tags: KDE PIM

Differential Revision: https://phabricator.kde.org/D29531