Support opening new sessions in current working dir

Summary:
When a Konsole profile has the "Start in same directory as current session"
setting enabled, Yakuake now respects the setting and opens new sessions
in the current working dir, just like Konsole would.

BUG: 396472
FIXED-IN: 20.04.0

Reviewers: hein, #yakuake, #konsole, tcanabrava, hindenburg, mweepigeon, ngraham

Reviewed By: mweepigeon, ngraham

Subscribers: ngraham, mweepigeon, ryanmccoskrie

Differential Revision: https://phabricator.kde.org/D26744