Fix correct location of RFE IMU for iCub 2.6 models

[traversaro]

To correctly run WBD for robots that have a 2.6 version of the head, we need to correctly export the iCub models with the correct location of the imu_frame frame. To avoid the need to re-generate a simmechanics model, we can do something similar to https://github.com/robotology/icub-model-generator/pull/139 in which a new iCubGazeboV2_7 model is added with just modification at the configuration/CMake level.

[traversaro]

See https://github.com/robotology/icub-main/issues/570 .

[traversaro]

Once this is done, we should properly generate (or simply install) for the following robots that have RFE head:

• iCubGenova07
• iCubHongKong01
• iCubGenova08

[Nicogene]

For changing the pose of the frame of the IMU without passing through the cad we needed to add an option in the simmechanics-to-urdf script:

https://github.com/robotology/simmechanics-to-urdf/pull/42

[Nicogene]

PR opened for producing the icub V2_6 model https://github.com/robotology/icub-model-generator/pull/164

[Nicogene]

This should be done, closing