JSON supports UTF-16, however the serializer is 8-bit clean. Instead of
returning a QString only to turn it back into a QByteArray, return a
QByteArray on serialization.
Turns Response into a QObject and sets parent to the
command that emits it.
Each Command is also a child of the decorator commands,
Timeout and PageLoading commnds, so that deleting the
top level command will delete all the children.
See discussion in #430.