Skip base64 encoding of QDataStream, avoid temporary QByteArray

Summary:
There is no need to do any Base64 encoding of the data. Also avoid
streaming the data to an intermediate QByteArray, but directly stream
to stdout.

Test Plan: PATH=pwd/bin/:$PATH ctest

Reviewers: Frameworks, Baloo, astippich, ngraham

Reviewed By: Baloo, ngraham

Tags: Baloo

Differential Revision: https://phabricator.kde.org/D19202