Remove dh-based generator for old iCub models

[traversaro]

To get rid of the legacy code contained in https://github.com/robotology/icub-model-generator/tree/master/dh, a possibility is to generate all hte possible combination of the models that can be obtained via icub_urdf_sdf_from_dh_generator command (see https://github.com/robotology/icub-model-generator/blob/master/dh/generator/icub_urdf_sdf_from_dh_generator.cpp), in particular for the binary options:

• headV1/headV2
• armsV1/armsV2
• legsV1/legsV2
• feetV1/feetV2

So we should obtain 16 URDF models with this naming:

• icub-legacy-urdf-headV1-armsV1-legsV1-feetV1.urdf
• ...
• ...

Once we have that, the CMake macro generate_icub_dh should simply copy the appropriate model and install it.

[traversaro]

This will be solved by #171 and a following cleanup PR. See also the related issue #96 .