[contacts] Populate remoteId of newly created contact

Summary:
If user tries to modify a contact that has just been created, the modify job returns 404.
Although `remoteId` gets updated by `changeCommitted`, the UID inside Addressee doesn't.
We need to update the payload explicitly, in order to resolve the confusion

This patch adds an `ItemModifyJob` which does precisely that.

Test Plan:
 1) Create contact in KAddressBook
 2) Check Web: contacts is created
 3) Change this contact inside KAB
 4) (without patch) Contact does not get changed inside Web UI, we get 404
 5) (with patch) Contact gets changed

Reviewers: dvratil

Reviewed By: dvratil

Subscribers: kde-pim

Tags: #kde_pim

Differential Revision: https://phabricator.kde.org/D28179