Add PCD exporter for pointclouds that are not generated by blensor

[mgschwan]

PCD files can be exporter during the scanning process but after a pointcloud has been added to a scene it can not be exported to PCD anymore.

TODO: Add export addon to PCD. However, this exporter will be limited to pointclouds and not usable for real meshes.

[balzer82]

I am using following code to get them out:

for item in bpy.data.objects:
    if item.type == 'MESH' and item.name.startswith('Scan'):
        # Scannerpunkte durchgehen
        for sp in item.data.vertices:
            print('X=%+#5.3f\tY=%+#5.3f\tZ=%+#5.3f' % (sp.co[0], sp.co[1],sp.co[2]))