Typos : replace acutal by actual and acutally by actually

There are some typos in Moodle code, in some comments. So acutal should be replaced by actual and acutally by actually.

Correcting these errors won't change the way Moodle works, but i feel it's always better.

It's possible to find corresponding files with this command :

grep -rne 'cutal' path/to/moodle

In mod/quiz/accessrule/accessrulebase.php, easist should also be replaced by easiest