GUI: Support styles in xml to reduce xml file size

Also allow sliders to have their own text label instead of
requiring a whole separate text object for the label in the xml.

Change-Id: I6e314efb4bb454d496555ff7e003d743063a1308
diff --git a/gui/image.cpp b/gui/image.cpp
index 60b1cb9..8b43aaa 100644
--- a/gui/image.cpp
+++ b/gui/image.cpp
@@ -27,9 +27,6 @@
 
 GUIImage::GUIImage(xml_node<>* node) : GUIObject(node)
 {
-	xml_attribute<>* attr;
-	xml_node<>* child;
-
 	mImage = NULL;
 	mHighlightImage = NULL;
 	isHighlighted = false;
@@ -37,15 +34,11 @@
 	if (!node)
 		return;
 
-	child = node->first_node("image");
-	if (child)
-	{
-		mImage = LoadAttrImage(child, "resource");
-		mHighlightImage = LoadAttrImage(child, "highlightresource");
-	}
+	mImage = LoadAttrImage(FindNode(node, "image"), "resource");
+	mHighlightImage = LoadAttrImage(FindNode(node, "image"), "highlightresource");
 
 	// Load the placement
-	LoadPlacement(node->first_node("placement"), &mRenderX, &mRenderY, NULL, NULL, &mPlacement);
+	LoadPlacement(FindNode(node, "placement"), &mRenderX, &mRenderY, NULL, NULL, &mPlacement);
 
 	if (mImage && mImage->GetResource())
 	{