Add styles for nested "draw:*" elements when cloning master pages.

Previously only the top-level `draw:*` elements were styled.
What would you think about moving this loop out to below the `while (elementToClone)` loop, behind the `dropTemplateDrawFrames` call? To go over all new children of the created page in one go?
```
                elementToClone = masterPageElement.firstElementChild;
                while (elementToClone) {
                    if (elementToClone.getAttributeNS(presentationns, 'placeholder') !== 'true') {
                        clonedElement = /**@type{!Element}*/(elementToClone.cloneNode(true));
                        clonedPageElement.appendChild(clonedElement);
                    }
                    elementToClone = elementToClone.nextElementSibling;
                }
                // TODO: above already do not clone nodes which match the rule for being dropped
                dropTemplateDrawFrames(clonedPageElement);

                // position all elements
                clonedDrawElements = clonedPageElement.getElementsByTagNameNS(drawns, '*');
                for (j = 0; j < clonedDrawElements.length; j += 1) {
                    setDrawElementPosition(styleId + '_' + i + '_' + j, clonedDrawElements[j], stylesheet);
                }
```