Improve Job Dialog buttons' icons and text

Summary:
The buttons were on the wrong side of the window, lacked icons, and the affirmative
button said "run" which didn't match the verb used in the dialog's title "send".

This patch corrects those issues.

Test Plan:

Reviewers: nicolasfella, apol, GB_2, VDG

Reviewed By: nicolasfella, GB_2, VDG

Subscribers: kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D22055