Port more deprecated functions and fix warnings

Summary:
KFileItem(mode, permissions, ...) is deprecated.
Port deprecated KRun::run to KRun:runService.
Replace deprecated std::auto_ptr with std::unique_ptr.
Add Q_DECL_OVERRIDE to MainWindow::eventFilter.

Depends on D5750
Depends on D5751

Test Plan: Tests pass.

Reviewers: ltoscano, sandsmark, gateau

Reviewed By: gateau

Differential Revision: https://phabricator.kde.org/D5752