[gthumb-list] the new folder treeview

["Dr. Michael J. Chudobiak" <mjc avtechpulse com>]

I really like having the new treeview!

One suggestion: there can be a noticeable delay in loading subfolders 
when you click an expander. (I have noticed this in other software too.)

It would be nice to add a preloader to pre-populate the child folders of 
the displayed folders, to eliminate this delay. (Not images or files, I 
just mean folder names).

- Mike