Format: yapf 0.32

[cmake] Improve Eigen detection

- Avoid CMAKE_PACKAGE_REGISTRY
- Use Eigen3::Eigen if available

format

Fix optional pinocchio dependency

primitive now accepts initial variable for initialisation

Fix destructors, hidden virtual method

Update to pinocchio v2.6.0

ref https://github.com/stack-of-tasks/eigenpy/pull/226

Update CMakeLists.txt for pinocchio and Boost::serialization

cross_implementation was missing

curves → ndcurves, fix #2