ENH: Create a RocketPy file (.rpy) to store the project

[Gui-FernandesBR]

There's already some draft cod in the first hackathon repo

[ArthurJWH]

Summary:
This issue is related to the creation of a JSON file that encodes and stores the objects from a simulation. Currently, the decoder returns the original objects from the simulation. This poses a problem when it comes to the class Flight, since it creates the object calling the __init__() method, which takes time to resimulate.

Tasks:

• Create a resimulate attribute in RocketPyDecoder, with default being False
• Code an if statement to check if resimulate attribute is False and the class is Flight
• Create the object Flight inside the if statement with __new__() method and insert the simulation solution from the the JSON file
• Check if all_info() method still works
• Create a save_to_rpy() and load_from_rpy() functions in utilities
• Create new tests
• Document the new parameter