Add python version of SFMdata as gtsam.examples submodule

The gtsam.examples submodule should be loaded explicitely:
>>> import gtsam.examples

python/gtsam/examples/SFMdata.py

@@ -0,0 +1,32 @@
+ 
+  # A structure-from-motion example with landmarks
+  #  - The landmarks form a 10 meter cube
+  #  - The robot rotates around the landmarks, always facing towards the cube
+
+import gtsam
+import numpy as np
+
+def createPoints():
+	# Create the set of ground-truth landmarks
+	points = [gtsam.Point3(10.0,10.0,10.0),
+			  gtsam.Point3(-10.0,10.0,10.0),
+	          gtsam.Point3(-10.0,-10.0,10.0),
+	          gtsam.Point3(10.0,-10.0,10.0),
+	          gtsam.Point3(10.0,10.0,-10.0),
+	          gtsam.Point3(-10.0,10.0,-10.0),
+	          gtsam.Point3(-10.0,-10.0,-10.0),
+	          gtsam.Point3(10.0,-10.0,-10.0)]
+	return points
+
+def createPoses():
+	# Create the set of ground-truth poses
+	radius = 30.0
+	angles = np.linspace(0,2*np.pi,8,endpoint=False)
+	up = gtsam.Point3(0,0,1)
+	target = gtsam.Point3(0,0,0)
+	poses = []
+	for theta in angles:
+		position = gtsam.Point3(radius*np.cos(theta), radius*np.sin(theta), 0.0)
+		camera = gtsam.PinholeCameraCal3_S2.Lookat(position, target, up)
+		poses.append(camera.pose())
+	return poses

python/gtsam/examples/__init__.py

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+from SFMdata import *