“Un-rolls“ contents of current node: recursively replaces all repeating
children with their repeated clones
@param {AbbreviationNode} node
@returns {AbbreviationNode}
function unroll(node) {
		for (var i = node.children.length - 1, j, child, maxCount; i >= 0; i--) {
			child = node.children[i];
			
			if (child.isRepeating()) {
				maxCount = j = child.repeatCount;
				child.repeatCount = 1;
				child.updateProperty('counter', 1);
				child.updateProperty('maxCount', maxCount);
				while (--j > 0) {
					child.parent.addChild(child.clone(), i + 1)
						.updateProperty('counter', j + 1)
						.updateProperty('maxCount', maxCount);
				}
			}
		}
		
		// to keep proper 'counter' property, we need to walk
		// on children once again
		_.each(node.children, unroll);
		
		return node;
	}