Add support for logging categories
Summary:
Adds category logging to the KScreenLocker daemon/library and the greeter.
Replaces all current uncategorized messages with categorized ones in these
parts.
Test Plan: Tested messages with autotests and QT_LOGGING_RULES="kscreenlocker*=true".
Reviewers: Plasma, apol
Reviewed By: apol
Subscribers: apol, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D28389