Straight forward port from QJson to the native Json support.
As a note I have added 2 helper functions that make the code bit more
readable (object2qvariant and qvariatn2qobject).
Ported using KDELibs4Support, for a smaller delta, so we can keep
developing on master until we decide not to.
At the moment, it builds and installs but tests don't pass because
of a QCA2 initialization problem I didn't manage to debug yet.
CCMAIL: kdeconnect@kde.org