Let QObjectHelper also process child objects recursively
Let QObjectHelper also process child objects recursively

This now allows for full object hierarchy to be converted to and from
JSON. If the property for the subobject is a QObject-derived-pointer and
the QVariant value is a map (ie. a JSON subobject), QObjectHelper will
process that subobject recursively.

The downside is that this requires the metaobjects to be explicitely
registered before being first used (using `qRegisterMetaType<>()`) but
it's a small tradeoff.

mck182/RESTQtful,mck182/RESTQtful