XML: add utility method to get child elements

When you have an element, and want all child elements with the given
tag name, you can now call this handy new static utility method.

Author: ctrueden

src/main/java/org/scijava/util/XML.java

@@ -252,6 +252,13 @@ public static ArrayList<Element> elements(final NodeList nodes) {
 		return elements;
 	}
 
+	/** Gets the given element's specified child elements. */
+	public static ArrayList<Element>
+		elements(final Element el, final String child)
+	{
+		return elements(el.getElementsByTagName(child));
+	}
+
 	// -- Helper methods --
 
 	/** Loads an XML document from the given file. */