Typo in maturity topics. Usefullness --> Usefulness

Author: mliebelt

data-yml.php

@@ -108,7 +108,7 @@ function build_table_tooltip($array, $headerWeight = 2)
     $html .= "<div><b>" . gettext("Opportunity") . ":</b> " . $array['measure'] . "</div>";
     $html .= "<hr />";
     $html .= "<h$headerWeight>Exploit details</h$headerWeight>";
-    $html .= "<div><b>Usefullness:</b> " . ucfirst($mapUsefulness[$array['usefulness']-1]) . "</div>";
+    $html .= "<div><b>Usefulness:</b> " . ucfirst($mapUsefulness[$array['usefulness']-1]) . "</div>";
     $html .= "<div><b>Required knowledge:</b> " . ucfirst($mapKnowLedge[$array['difficultyOfImplementation']['knowledge']-1]) . "</div>";
     $html .= "<div><b>Required time:</b> " . ucfirst($mapTime[$array['difficultyOfImplementation']['time']-1]) . "</div>";
     $html .= "<div><b>Required resources (systems):</b> " . ucfirst($mapResources[$array['difficultyOfImplementation']['resources']-1]) . "</div>";