Add option to preserve symlinks and another command "s" to jump sub directories

Created by: statik213

1. Add an option to not de-reference symlinks when paths are added to the database. I make heavy use of symlinks within my file system and don't like jumping to the physical paths.
2. Add a shortcut "s" to jump to a sub-directory below the the current directory.

I wasn't comfortable porting these changes to zsh, I'll leave that to you.