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