It allows to create a QJsonArray instance in C++ by using
a similar expression to JSON. For example:
QJsonArray a = {1, 2, 4};
[ChangeLog][QtCore][QtJson] QJsonArray now supports
C++11 initializer lists.
Task-number: QTBUG-26606
Change-Id: Icc352e518d9649d24176c89e7113d200d5c50b0d
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>