Convert hard coded shortcuts to standard keys

Test Plan: Check all changed shortcuts on all platforms.

Reviewers: Dolphin, rizzitello, elvisangelaccio

Reviewed By: Dolphin, rizzitello, elvisangelaccio

Subscribers: anthonyfieroni, ngraham, elvisangelaccio, rizzitello, Dolphin

Differential Revision: https://phabricator.kde.org/D11048