Add support for Organization

Summary:
This commits implements the Organization data type as defined in
schema.org. Of the many fields available, just a select few are
available.

Test Plan: Ran unit test, passed.

Reviewers: vkrause

Reviewed By: vkrause

Subscribers: vkrause, KDE PIM

Tags: KDE PIM

Differential Revision: https://phabricator.kde.org/D11910