Introduce KF5AuthCore
Summary:
It's KF5Auth but without kauthobjectdecorator.cpp
This will allow us to link helpers just against KF5AuthCore making
the library tree they pull much smaller
Reviewers: apol
Reviewed By: apol
Subscribers: apol, kde-frameworks-devel
Tags: Frameworks
Differential Revision: https://phabricator.kde.org/D18610