Add Objective-C specific type converters to QUuid.

This patch adds the Objective-C NSUUID/CFUUIDRef converters to QUuid

[ChangeLog][QtCore][Objective-C] Added NSUUID/CFUUIDRef converters for
QUuid

Change-Id: Ifebf6fd5ce9f46dcdc06f221e189cb1fd9079e18
Reviewed-by: Jake Petroules <jake.petroules@theqtcompany.com>