Add --imgbox and --imginputbox support for KDialog

Summary:
I have added 2 new options for Image Box and Image Input Box in KDialog because I did not find any.

Here is how they look.

Reviewers: KDialog, dfaure

Reviewed By: KDialog, dfaure

Subscribers: dfaure, KDialog

Tags: KDialog

Differential Revision: https://phabricator.kde.org/D17895