stop, next file, previous file buttons along with the added feasures the
buttons represent. i've also added png versions of all of the icons just
in case the svg versions are not practical to use. i also fully built
out a tray icon functionality so the application can now minimize to
system tray. also updated the app logo to a new flat icon type sinewave
look. then finally, i've added the restore button to the tray icon so it
will restore the window back in front from the tray.
