v0.3.10-beta1

• For runners, exposed timestep parameter that controls the delta time of the simulations. Lower number generally means higher accuracy. Implemented for Mujoco only; Isaac Gym ignores this setting for now. Changed default from previously hard-coded value to a setting more reasonable for CI-Group's general use-case.
• Added armature to active hinge(hard-coded, just like other joint parameters currently). Set to a reasonable value to CI-Group's general use-case. This should significantly improve realism for not-smooth controllers.
• Added a mapping function from actor state(result from simulation) to modular robot body state. Currently only implemented for the core. Previously the examples directly used the first rigid body of the actor state. This indeed equated to the core, but this new function abstracts away the need to interact with the actor state directly and makes everything more future proof. E.g. if we want to use the state of other modules or if we want to lazy load simulation results.
• Fixed a bug in Mujoco runner where initial robot orientation was incorrect.
• Fixed some unimportant warnings in CI.