Modified ActorFrame:GetChildren to actually return all children.

In cases where multiple children had the same name, only the last one would be in the table returned by GetChildren, and only the first one would be returned by GetChild.
This pull request changes both to return a table in the case where multiple children have the same name.
The table that is returned also acts as a pass-through layer to the the last child of that name, so that old code doesn't need to be updated.
The benefit is that new code can easily access all children of the same name.