Misc/Cleanup

* moving commonly used strings to defines
 * moving commonly reused/similar page generation functions to the parent
 * generally using consistent return types, more type hints and less strings
 * prevent browser context menu when right clicking on UI elements with their own context menus
 * fixed menu path for icons

includes/ajaxHandler/profile.class.php

@@ -217,7 +217,7 @@ class AjaxProfile extends AjaxHandler
             return;
         }
 
-        $this->contentType = 'image/'.$matches[2];
+        $this->contentType = $matches[2] == 'png' ? MIME_TYPE_PNG : MIME_TYPE_JPEG;
 
         $id   = $matches[1];
         $dest = imageCreateTruecolor($sizes[$s], $sizes[$s]);