Replace all qWarning and related calls with categorised logging
This replaces all uncategorised qWarning() calls with calls to qCWarning(), using the
kf5.ki18n category for the main warnings, with kf5.ki18n.kuit used for warnings
produced by the kuit code.
Test Plan: Tests still pass, warnings printed by ki18n during tests now use categorised logging.
Reviewed By: apol
Differential Revision: https://phabricator.kde.org/D24630