You may safely delete the old js/addons/kl/editor-manager.
Added compatibility for the Math add-on from @CMTV.
Added a new "remove all links" button, that can be applied in the toolbar layout section. If clicked, it will remove all existing links in the current editor instance (leaving the link content intact).
Changed the character counter styling to work as style property.
You can find the new style property under Rich Text Editor -> Character Counter.