Port away from QtWebKit to QtWebEngine
Summary: QtWebKit is unmaintained
Test Plan: manual testing
Reviewers: KDevelop, mwolff, kfunk
Reviewed By: KDevelop, kfunk
Subscribers: kfunk, mwolff, antonanikin, kdevelop-devel
Differential Revision: https://phabricator.kde.org/D5041