[FIX] website_slides: various fixes

Display
 * improve color of trophy displayed on top of course main page (success if
   course done, warning while working on it);
 * correctly fetch and display karma/xp points on course lesson list. It is
   either gain of next try, either awarded points depending on slide
   completion;
 * fix control buttons in course main page (prev, next, set done,
   set completed, fullscren), notably correctly set them disabled;

Linting / Code
 * put demo in no update;
 * rename some parameter in website_slides_survey to avoid conflict between
   quiz (on a slide) and certification (a survey);

 Commit linked to task ID 1941250 and PR #31697.

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>