basic.py: WriteESConfig() swap a and b

BTN_DOWN  = B (SNES) = X (PS3) = OK
BTN_RIGHT = A (SNES) = O (PS3) = Cancel
set_ES_updateinput(): fix d-pad buttons
RetroArch : disable config_save_on_exit

Retroarchs defaults changed. config_save_on_exit is enabled by default now. 
https://github.com/libretro/RetroArch/commit/dd16f124704f33bf277401dd9cb6a16d1684a8a7
Merge pull request #297 from gizmo98/master

Fix some minor problems