codyco-superbuild does not build KDL by default anymore

[traversaro]

Since iDynTree 0.8, KDL is no more necessary. All the features previously depending on KDL has now been reimplemented by using iDynTree-only classes. See here for the original discussion on why iDynTree has dropped KDL.

As a consequence, by default the codyco-superbuild no longer requires KDL (and its dependencies such as urdfdom and urdfdom-headers).
In case, for backward compatibility, one wants to enable the support to KDL, it suffices to enable the CODYCO_USES_KDL option that can be found in the advanced settings.
Note that on macOS we no longer support building urdfdom and urdfdom-headers through the super build. Users should explicitly install them, e.g. by using homebrew (brew install ros/deps/urdfdom).

cc @robotology/codyco-developers