Bad configuration file management

If configuration file can't be opened or is bad, a new one is created with
default settings. If this is impossible for some reason, program quits
nicely (close SDL).
Default config modification

Old default config was "European": keys were "left to right". On snes, buttons
are "right to left":

L                      R
   ^
   |                 X
<-- -->           Y  A
   |              B
   v

new mapping (still for qwerty keyboard):
    A -> d
    B -> s
    X -> e
    Y -> w
    L -> a
    R -> f
START -> space
SELECT-> left control
ACCEL -> backspace
QUIT  -> escape