TODO

========================= GUI
[x] menubar (fring,help)
    [x] refresh
    [x] save to file
    [x] select directory
    [x] show hidden files
    [x] "about" dialogue
    [x] open parent folder

[x] click on folder -> open it
[x] show busy cursor while walking dir tree
[x] do not show black backrgound when app starts up
[ ] don't reload the busy cursor when it's already set

========================= DISPLAY
[x] display total in ring center 
[ ] always render text on top
[ ] make sure that filenames are always visible
[ ] do more magic adjustments
[ ] clean gui -> renderer interface

========================= FOLDER READING
[ ] merge back c_walker
[ ] don't use size, use blocks of 512k instead
    (this will solve a couple of long/int bugs)