Add more parabolic functions and make application command line

Turn the application into a command line application that takes in the filename or string as argument along with the function used to encrypt or decrypt(can be one among list of options) and then returns the output.

Start by locating the current application entry point and the existing list of parabolic encryption and decryption functions. Determine how the program currently receives input, then define the command-line arguments for a filename or string and a selected function. Done means the command accepts those inputs and returns the corresponding encrypted or decrypted output.

Scritto dal modello di indicizzazione a partire dal testo della issue.