expand/collapse action by right/left arrow key?

[Kang Jeong-Hee <Keizi mail co kr>]

you may know Expolrer file manager of Windows.
the tree support to expand or to collpase nodes by right/left arrow key.
it is much of performance to navigate by only four arrow keys.

this time being, plus/minus work to expand/collapse.
what do you think of this?


Thanks. :)