Use correct color and font when exporting to HTML

Summary:
Instead of using only the default colors (and white background),
use the correct colors and font from the profile, if available. If
not exporting with a profile, it falls back to the old behavior
(i. e. when copying to clipboard).

Reviewers: hindenburg, #konsole

Reviewed By: hindenburg, #konsole

Subscribers: ngraham, konsole-devel, #konsole

Tags: #konsole

Differential Revision: https://phabricator.kde.org/D16227