…spawn_actor.launch` for spawning Actors without modifying the existing world files [#59]

…arking` world

…izer list

]

- note: also got rid of `<functional>` from .cpp includes (locally only)

…lbacks

…locked in the action feedback callback (only for some time)

- increases the robustness of finishing complex tasks relying on navigation
- somehow related to [#38]

… easier time management in the scenarios

…m the living room scenario

- adjusted utilizing the recent upgrades

…execution performed in a separate thread [#29, #57]

…eaded task execution

… `computePlan` method

…ort holonomic actors [#31]

…ormation to support holonomic actors

- related to [#31]

…s` method

… class

…iours earlier

…example.launch`

…uBeRo` actors operating with predefined trajectories (without online perception)

…launch` made configurable [#59]

…figuration via `example.launch`