Unexport protected methods only needed internally here

Summary:
This will allow us to eventually hide those entirely on the private class
without breaking the ABI. Also, use unique_ptr rather than QScopedPointer
here for consistency among the public classes.

Reviewers: ervin

Subscribers: kde-pim

Tags: #kde_pim

Differential Revision: https://phabricator.kde.org/D28562