#28 Add maximum folder count to AutoClose.

[Leif Olson]

Rather than having AutoClose just be a true and false
option, I think that it would be very handy if you
could set it to 2 or 3, so that you could keep the last
couple of folders open, but then start autoclosing
folders after a certain point. This would make it very
easy if you wanted to switch frequently between nodes
in 2 different folders.
Another way that this could be handled is that you
could set a limit of how many total folders and nodes
can be displayed so that after this limit is exceeded,
the oldest open folders would be closed until the total
goes under the limit again.