Summary:
Don't use QDBusConnection::ExportAllContents
No need to make connect and receivedPackage public slots (they're are the
parent's already)
Fixes T4975
Test Plan: Rough manual test
Reviewers: #kde_connect, albertvaka
Reviewed By: #kde_connect, albertvaka
Maniphest Tasks: T4975
Differential Revision: https://phabricator.kde.org/D3871
Makes it possible to specify the different properties sent at once,
rather than one by one as we used to do.
Also port whenever possible to the initializer-list syntax.
REVIEW: 128269
