Qt container-based classes now require stream operators

Since commit 5f542f3cca13f2da58b82aee2efbaffefeee00a7 Qt container-derived classes, such as

class UIntList : public QList<uint>

now can not be streamed to/from QDBusArgument.

error: no match for 'operator>>' (operand types are 'QDBusArgument' and 'UIntList')

http://doc.qt.io/qt-5/qdbusargument.html#qDBusRegisterMetaType says:

If T isn't a type derived from one of Qt's container classes, the operator<< and operator>> streaming operators between T and QDBusArgument must be already declared.

Thus, the change seems to contradict with the documentation and breaks various projects, e.g. TelepathyQt: https://bugs.freedesktop.org/show_bug.cgi?id=95376