#10 Allow subnodes to use different layouts

[Neil Ernst]

It would be useful to allow a subnode, in nested view,
to display all its children in flat layout, such as
spring or tree. This would help with scaling as well,
as you could view portions of a tree in different layouts.

Would probably have to decide what to do with arcs that
go outside the node - perhaps just doing a menu option
that displays the subnodes in a tree using the is-a
relationship (or whatever the current cprel is).