Modify origin of assigned collisions for sole links

In #158 the location
of the frames of the links of the soles ( (r|l)_foot_(front|back) ) have been
moved to the origin of the FT sensors that connect them with the (r|l)_ankle_2
link. All the quantities expressed in this frame have been automatically modified
to account for its new location by the simmechanics-to-urdf script, except
for the location of the assigned collision, that are hardcoded in the .yaml file .
This created a regression, has it effectly moved the sole assigned collisions up,
so the robot was actually touching the ground with the (r|l)_ankle_2 links, that
do not have any contact parameter assigned.

This commit fixes the situation by taking the existing z value of the assigned
collision origin, and adding the offset with which the other elements
(visual, inertial) have been modified (see aae9cd6#diff-4a8f86568a5c3c3a54aa41e5ae088cbcb40bbfd3a63077a9d2c760840494cf1fL239),
to obtain:
newCollisionZ = oldCollisionZ + (newVisualZ - oldVisualZ)
              = 0.003         + (0.9335     - 0.9558    )
              = -0.0193

urdf/simmechanics/CMakeLists.txt

@@ -123,22 +123,22 @@ macro(generate_ergocub_simmechanics)
     geometricShape:
       shape: box
       size: 0.117 0.100 0.006
-      origin: \"0.0 0.0 0.003 0.0 0.0 0.0\"
+      origin: \"0.0 0.0 -0.0193 0.0 0.0 0.0\"
   - linkName: r_foot_rear
     geometricShape:
       shape: box
       size: 0.117 0.100 0.006
-      origin: \"0.0 0.0 0.003 0.0 0.0 0.0\"
+      origin: \"0.0 0.0 -0.0193 0.0 0.0 0.0\"
   - linkName: l_foot_front
     geometricShape:
       shape: box
       size: 0.117 0.100 0.006
-      origin: \"0.0 0.0 0.003 0.0 0.0 0.0\"
+      origin: \"0.0 0.0 -0.0193 0.0 0.0 0.0\"
   - linkName: l_foot_rear
     geometricShape:
       shape: box
       size: 0.117 0.100 0.006
-      origin: \"0.0 0.0 0.003 0.0 0.0 0.0\"
+      origin: \"0.0 0.0 -0.0193 0.0 0.0 0.0\"
 ")
     endif()
 
@@ -149,22 +149,22 @@ macro(generate_ergocub_simmechanics)
         geometricShape:
           shape: box
           size: 0.117 0.100 0.006
-          origin: \"0.0 0.0 0.003 0.0 0.0 0.0\"
+          origin: \"0.0 0.0 -0.0193 0.0 0.0 0.0\"
       - linkName: r_foot_rear
         geometricShape:
           shape: box
           size: 0.117 0.100 0.006
-          origin: \"0.0 0.0 0.003 0.0 0.0 0.0\"
+          origin: \"0.0 0.0 -0.0193 0.0 0.0 0.0\"
       - linkName: l_foot_front
         geometricShape:
           shape: box
           size: 0.117 0.100 0.006
-          origin: \"0.0 0.0 0.003 0.0 0.0 0.0\"
+          origin: \"0.0 0.0 -0.0193 0.0 0.0 0.0\"
       - linkName: l_foot_rear
         geometricShape:
           shape: box
           size: 0.117 0.100 0.006
-          origin: \"0.0 0.0 0.003 0.0 0.0 0.0\"
+          origin: \"0.0 0.0 -0.0193 0.0 0.0 0.0\"
       - linkName: r_hip_1
         geometricShape:
           shape: box