Make public way to append created Grid/Scheduler/Gantt to DOM element

[SergeyMaltsev]

https://www.bryntum.com/forum/viewtopic.php?f=51&t=19296&p=95391#p95391

Currently Scheduler which was created without appendTo/adopt config option can be appended to DOM element with

document.getElementById('container').appendChild(scheduler.element);

or

DomHelper.append(document.getElementById('container'), scheduler.element);

but this also require private render() call to make it visible

scheduler.render();

Also this code below doesn't work

WidgetHelper.append(scheduler, document.getElementById('container'));

Changelog

Added support for changing widget's appendTo, insertBefore and insertFirst at runtime