#2 Saving/loading of child area's tabs

When a layout is saved, Tabs of each Area are saved with its unique index (ie. Var34). Currently, the XML does not know whether this tab belongs to the Area itself or its ChildArea. Suppose a layout is modified so that an Area's RightTab is aligned to the LeftTab of another Area's ChildArea. However, when we load the XML, it won't know that this Tab is a ChildArea's tab. In turn, a new Tab will be created, which is different to the childArea's Tab created by setHAlignment(), setMargin() methods. This leads to an incorrect layout being loaded.