[pocolibs] ability to use DepthCamera as Velodyne

to be used as:
```python
self.velodyne = DepthCamera()
self.velodyne.translate(x = 0.5, z = 0.35)
self.velodyne.rotate(y = -1.57)
self.velodyne.properties(cam_near = 0.5, cam_far = 50)
self.velodyne.properties(cam_width=128, cam_height=128)
self.append(self.velodyne)
self.velodyne.add_stream('pocolibs',
    'morse.middleware.pocolibs.sensors.velodyne.Velodyne3DImage',
    poster = 'velodyneThreeDImage')
```