Enhancement: Resource tomboynotes updates its content automatically

Summary: The resource uses now an update interval for updating its content automatically. The default is 5 minutes.

Test Plan:
I've tested it already in my development VM.

Its implemented like in the DAV resource.

Reviewers: dvratil, #kde_pim, knauss, vkrause

Reviewed By: dvratil, #kde_pim

Subscribers: lbeltrame, mlaurent, #kde_pim

Tags: #kde_pim

Differential Revision: https://phabricator.kde.org/D7862