function createSVG(oContainer) {
		var oSvg = document.createElementNS(SVG_NAMESPACE, 'svg'),
			oRect = oContainer.getBoundingClientRect(),
			fWidth = oRect.width,
			fHeight = oRect.height;

		oSvg.setAttribute('viewBox', '0 0 ' + fWidth + ' ' + fHeight);

		oSvg.setAttribute('class', 'overlay');

		oContainer.appendChild(oSvg);

		return oSvg;
	}
@param oContainer {Node} node an HTML DOM to which the overlay should be attached
@return {SVGSVGElement}