Improved UI/UX

[jo11he]

This is a suggestion to rethink the user interaction with the data downloader class. As of now, there are some cases (Cassini, or flyby missions in general) for which the user has to write a short script, execute the script and then interact with the terminal to get the desired downloads. I would suggest instead to make two separate paths of interaction for the user:

1. User gets the job done in one script (also for Cassini). Import class, create instance, call get_data function and then specify timespan or flybys (how to implement this is up to creativity of the developer)

2. Additionally (bit more elegant) there could be an executable that can be called from terminal, where the user is prompted to give (in sequence) the inputs to obtain the desired output (mission name, time bounds, archive path). The prompts can be different based on prior inputs.