New contact

[tkoolen]

On top of #577. I eventually want to merge this, but it'll take some time. These are all old commits. This will be part of a new major release.

To do (probably an incomplete list):

• [ ] ensure that deps that are in our control have RigidBodyDynamics 2 upper bound.
• [ ] re-enable all tests
• [ ] add compat bounds for new dependencies
• [ ] sort using/import statements in Contact.jl
• [ ] consistent file names
• [ ] Move CoordinateTransformations <-> RigidBodyDynamics type conversions to a better place
• [ ] Actually use the GJK stuff (currently just supporting HRep of polyhedral collision geometry, only efficient for low-dimensional polyhedra). Possibly need to add EPA to EnhancedGJK.jl for this
• [ ] Actually use CatVector (in ODE integration, to separate contact state from MechanismState).
• [ ] Benchmarks: simulating multiple mechanisms.
• [ ] benchmarks: contact
• [ ] Documentation / update examples