Display emblem over mime icon if torrent has error(s) to indicate the
issue.
Use normal text color instead of red when drawing selected item: there
is no easy way to be sure that red color looks nice on selection
background, and most of the time it doesn't. Using red color for non-
selected items is questionable too, but let's leave it at that for now.
Among other things,
* fix turtle icons size (20x14 -> 16x16)
* use QIcon states instead of changing the turtle icon ourselves each
time (unchecked - off, checked - on)
* make speed limit action in tray menu checkable
* simplify status bar buttons drawing and use QToolButton instead of
QPushButton
Mike Gelfand