MDL-44216 Atto: Reversing the indent outdent buttons
MDL-44227 Atto: the screenreader helper now displays some texts when alt or title don\'t exist
MDL-44228 add Atto sub-plugins admin table
MDL-44228 editor_atto: added missing outdent icon
MDL-44040 editor: implemented shortcuts for bold, italic, underline and undo