Remove dead code in TerminalDisplay

Summary:
A lot of methods that no one called, a lot of methods that the
only calee could be removed to a direct call.

Reviewers: #konsole, hindenburg, ngraham

Reviewed By: #konsole, hindenburg

Subscribers: sandsmark, konsole-devel

Tags: #konsole

Differential Revision: https://phabricator.kde.org/D18520