Slider title needs to support multi-lang filter

[gjb2048]

Ref: https://moodle.org/mod/forum/discuss.php?d=344688

Possible solution from Paul:

`changing line 295 in essential\classes\toolbox.php to

$slidetitle = self::get_setting('slide'.$slideno, 'format_html');

instead of

$slidetitle = self::get_setting('slide'.$slideno);`

[gjb2048]

Gone with:

format_string(self::get_setting('slide'.$slideno));

as html could get messy.