support for toggling by CSS selector, not only id (#210)

this is useful eg. for controls manually rendered as table cells `<td>` which have only `<tr>` valid parent .. if there are multiple cells within table row toggling via `id` is not feasible (it would toggle all the cells in that row).

src/assets/netteForms.js

@@ -655,9 +655,12 @@
 	 * Displays or hides HTML element.
 	 */
 	Nette.toggle = function(id, visible, srcElement) { // eslint-disable-line no-unused-vars
-		var elem = document.getElementById(id);
-		if (elem) {
-			elem.style.display = visible ? '' : 'none';
+		if (/^\w+$/.match(id)) { // id
+			id = '#' . id;
+		}
+		var elems = document.querySelectorAll(id);
+		for (var i = 0; i < elems.length; i++) {
+			elems[i].style.display = visible ? '' : 'none';
 		}
 	};