This program corresponds to the 5th project of the OpenClassrooms Python apps dev.

The program is designed to allow an user to ask for substitution for any common food element
they want to replace in order to have a healthier lifestyle. The program will use the openfoodfacts 
API and will allow the user to retrieve any past substitution they have done.


At first the user is asked a question about wether he wants to find a substitution for an element
or to go back to his saved searches.

For the substitution option a list of the 20 biggest categories is displayed with an associated
number between 1 and 20.
The user can indicate the category number he wishes to go through.
He can also, by selecting 0 display 20 more categories and so on.

After selecting the desired category, the program displays a list of 20 (if posible) sub-categories
with the same choices posible.

Once selecting the category a list of elements within this category is displayed, sorted by 
nutrition grade.