Update models and worlds

[diegoferigo]

• Remove the sdf file of models that can be imported correctly in Ignition Gazebo from the urdf (CartPole, Pendulum).
• Convert the iCubGenovaV2_5 model (still unsupported but used for internal testing) with a recent sdformat. The new sdformat library does no longer convert urdf to sdf with the use_parent_model_frame tag, making the sdf compatible also with pybullet (I didn't test it yet).
• Manually added the material properties to the iCubGenovaV2_5 model as reported also in Investigate color support in mesh files #31 (comment).
• Removed all the unsupported sensors from iCubGenovaV2_5 model.

On the long run it would probably make more sense to keep only SDF files. There are a lot of nice features being released that will simplify the robot description. Though, the upcoming controllers will use iDynTree, that supports only URDF. I'd like to reduce the duplication, and since now Gazebo can parse our URDFs without any problem for the time being let's keep only URDFs.

In the future, as soon as the upstream sdf -> urdf conversion will be finalized, we can think of switching back to sdf.

[traversaro]

• Convert the iCubGenovaV2_5 model (still unsupported but used for internal testing) with a recent sdformat. The new sdformat library does no longer convert urdf to sdf with the use_parent_model_frame tag, making the sdf compatible also with pybullet (I didn't test it yet).

Related issue: robotology/icub-models#12 .

[traversaro]

Though, the upcoming controllers will use iDynTree, that supports only URDF. I'd like to reduce the duplication, and since now Gazebo can parse our URDFs without any problem for the time being let's keep only URDFs.

In the future, as soon as the upstream sdf -> urdf conversion will be finalized, we can think of switching back to sdf.

We can also think to switch to sdf only if iDynTree will support loading SDF directly (see robotology/idyntree#481).