mod_files.sh patch

There's a script, mod_files.sh, in ext/session for creating directory tree with depth X for sessions. As it stands, it's pretty poorly documented and very basic. I got exceptionally bored and rewrote most of it, the patch is attached. It runs fine for me in linux (with sh version 4.0). I don't have any other *NIX systems to test it out on, so I can't verify that it works in anything but linux, sorry. What I changed: 1. Usage now properly reflects arguments, and is better explained. 2. Will create directory given if it doesn't exist 3. Will hop into interactive select if directory already has contents 4. Switched from "test" to "[[ ]]" as it's easier to read and _should_ be just as supported.

Attachment: [text/x-patch] mod_files.diff