update diffbot base values; add colored wheel stl

Author: fjp

config/diffbot/base.yaml

@@ -1,6 +1,7 @@
 base:
   mass: 2.5               # Base mass in Kg
   x_size: 0.195           # Dimension in x axis
-  y_size: 0.198           # Dimension in y axis
-  z_size: 0.182           # Dimension in z axis
+  y_size: 0.08           # Dimension in y axis
+  z_size: 0.005           # Dimension in z axis
   mesh: 'chassis.stl'  # Name of the mesh files. Leave it empty ('') to have a white base.
+  #mesh: ''

config/diffbot/front_wheel.yaml

@@ -2,7 +2,7 @@ wheel:
   mass: 0.01        # Wheel mass in Kg
   radius: 0.011     # Wheel radius in m
   length: 0.006     # Wheel length in m, considering is as a cylinder
-  mesh: 'wheel.stl'          # Name of the mesh files. Leave it empty ('') to have a red wheel
+  mesh: 'wheel-colored.stl'          # Name of the mesh files. Leave it empty ('') to have a red wheel
   x_offset: 0.035
   y_offset: -0.056
   z_offset: 0.008