Update contributing authors list.
Update copyright date for recently added files.
Use more descriptive head depth sensor name.

- Remove hardcoded _rgbd suffix, let name parameter set it.

- Name parameter changed to head_mount_xtion, instead of head_mount_rgbd, as
  confusing topic names were appearing, eg. head_mount_rgbd_rgb.
Remove code duplication.

When launching reem with the head-mounted ASUS Xtion Pro Live, include the file
containing the stock REEM, instead of duplicating its contents.
Update ASUS Xtion Pro Live model.

- No longer compensate mesh non-standards compliance in URDF:
  - Scale mesh to meters.
  - Re-orient mesh origin.

- Make visualization texture darker.

- Use box collision geometry instead of a more expensive convex decomposition.
.
Rename ASUS sensor files and folders consistently.
Workaround Gazebo 1.0.2 bug with RGBD sensors.

There seems to be interference between the collision geometry and the camera image
and generated pointclouds of the ASUS xtion pro live sensor.
Change sensor material properties.
Silence Gazebo startup warnings and errors.

- Add dummy inertia to links.
- Manually add missing expected collada atttribute to transparency element.