Reset scene from Simulator and Interface

[clement-moulin-frier]

Description

When loading a scene in the simulator, then running it, we often want to come back to the initial scene state. For now it means restarting the simulator server and interface. It will be useful if this could be done more easily, with both:

• A "Reset scene" button in the interface
• A method of the Simulator class (but maybe the load_scene method already does the job), that can be invoked from the Client.

Writing this, I actually think it is just a special case of being able to load a scene (on server and/or client side), so this could be part of #30 .