Added 69 objects from YCB dataset (o0001-o0069)

[Hanziscool]

Physical properties are obtained from http://www.ycbbenchmarks.com/wp-content/uploads/2015/09/object-list-Sheet1.pdf.
Texture, density, geometry, color are obtained from the objects picture in the pdf.

[rojas70]

Please add more details:

1. Explain if you have import the actual XML and visual XML files and where.
2. Explain name conventions
3. Describe these changes are contained in the .xlsx file
4. Describe if any code accompanies these objects in .xml_objects and robosuite/robosuite/models/objects/init.py. If not state this is the next step to be done.

Thanks