drop windows support, add small image wrapper

The code will now work if only PIL is available, but also use
GraphicsMagick if possible.
displayer: speed up animations a little
renderer: minor cleanups
displayer: cleanup
mcomix: minor smart_scroller cleanup
comic_book: cleanup
displayer: use pygame get_default_font to get fallback font
improve command line arguments support

- use argparse to handle options/arguments
- pass the list of comics to the displayer
- automatically load the next/previous comic in the list on page change
  beyond the last/first page
comic2acv: remove leftover debug print
comic_book: cleanup
cleanup imports
comic_book: fix non-ascii support in archive paths
mcomix: cleanup i18n
displayer: add bindings to flip to next/previous comic
cplayer: sort (alphanumeric) the list of comics
comic_book: d'oh! fix priority extraction...
mcomix: improve worker thread stop implementation

Add support for stopping without flushing the orders queue: will wait
for all orders to be processed before stopping.
displayer: close comic in the background

So we don't delay loading the new comic.
displayer: improve flip to previous comic

- 'flip_comic(-1)' action: load previous comic, first page, first row
- 'flip_page(-1)' action on the first page: load previous comic, last page, first row
- 'navigate_row(-1)' on the first page, first row: load previous comic, last page, last row
mcomix: add right-to-left support to smart_scroller