Add new transform tutorial to appropriate classes

(cherry picked from commit e83af5dfc6)

doc/classes/Basis.xml

@@ -8,6 +8,7 @@
 		For such use, it is composed of a scaling and a rotation matrix, in that order (M = R.S).
 	</description>
 	<tutorials>
+		http://docs.godotengine.org/en/latest/tutorials/3d/using_transforms.html
 	</tutorials>
 	<demos>
 	</demos>

doc/classes/Quat.xml

@@ -10,6 +10,7 @@
 		It can be used to perform SLERP (spherical-linear interpolation) between two rotations.
 	</description>
 	<tutorials>
+		http://docs.godotengine.org/en/latest/tutorials/3d/using_transforms.html#interpolating-with-quaternions
 	</tutorials>
 	<demos>
 	</demos>

doc/classes/Transform.xml

@@ -8,6 +8,7 @@
 	</description>
 	<tutorials>
 		http://docs.godotengine.org/en/3.0/tutorials/math/index.html
+		http://docs.godotengine.org/en/latest/tutorials/3d/using_transforms.html
 	</tutorials>
 	<demos>
 	</demos>