Add icons to Edit menu

Summary:
Since Breeze offers such a great palette of action icons I thought we should make use of them which make things also more consistent with other applications.

Before:
{F5711158}

After:
{F5711159}

Test Plan:
Show menubar
Icons are shown in Edit menu

Reviewers: #dolphin, ngraham

Reviewed By: #dolphin, ngraham

Subscribers: ngraham

Differential Revision: https://phabricator.kde.org/D10503