Create logging categories via CMake

Summary:
Also set a consistent naming structure and to be only Info+ by default.

This may mean you need to update your logging rules if you want debug
output.

Reviewers: Plasma, hein

Reviewed By: Plasma, hein

Subscribers: graesslin, plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D1956