Add support for tutorial links to makerst.py

Also change the <tutorials> structure to make use of individual <link> tags

doc/classes/Transform.xml

@@ -7,8 +7,8 @@
 		Represents one or many transformations in 3D space such as translation, rotation, or scaling. It consists of a [Basis] "basis" and an [Vector3] "origin". It is similar to a 3x4 matrix.
 	</description>
 	<tutorials>
-		http://docs.godotengine.org/en/3.0/tutorials/math/index.html
-		http://docs.godotengine.org/en/latest/tutorials/3d/using_transforms.html
+		<link>http://docs.godotengine.org/en/3.0/tutorials/math/index.html</link>
+		<link>http://docs.godotengine.org/en/latest/tutorials/3d/using_transforms.html</link>
 	</tutorials>
 	<demos>
 	</demos>