Add TouristAttractionVisit

Summary:
This class is used to represent a "visit" to a specific place (e.g. a
monument).

Test Plan: Compile

Reviewers: vkrause

Reviewed By: vkrause

Subscribers: vkrause, KDE PIM

Tags: KDE PIM

Differential Revision: https://phabricator.kde.org/D12484