Add support for images embedded in the .acbf file

Summary:

• Add support for data and binary elements.
• Support loading images from embedded data.

Test Plan: Can read comics where the images are embedded in the .acbf file.

Reviewers: leinir, Peruse

Reviewed By: leinir, Peruse

Subscribers: leinir

Tags: Peruse

Differential Revision: https://phabricator.kde.org/D4295