Let auto-created stacks inherit the closability of their contents.
Let auto-created stacks inherit the closability of their contents.

Should fix #60

jcford73/golden-layout,LarissaSmith/golden-layout,golden-layout/golden-layout,Liplattaa/liplattaa-golden-layout,LarissaSmith/golden-layout,deepstreamIO/golden-layout,deepstreamIO/golden-layout,golden-layout/golden-layout,deepstreamIO/golden-layout,golden-layout/golden-layout,jcford73/golden-layout,Liplattaa/liplattaa-golden-layout