BUG: textnode is not removed from canvas

Text imported directly to the wrapper is not removed from the canvas with the component. 

To verify one can import simple texts multiple times to the demo and watch how they combine instead of replacing the previous one.

Adding this seems to help:

        editor.DomComponents.addType('textnode', {
            model: {
                removed() {
                    var el = this.getEl();
                    el.parentNode.removeChild(el);
                }
            }
        });

Tested with the demo v0.16.18.