Better command line argument parsing using decline

[YVbakker]

Summary

Currently the CLI arguments are only accepted in the format --key=value. Using a library such as (decline)[https://ben.kirw.in/decline] we can improve this.

Desired improvements:

• Space-based separation of argument and value
• Support for flags (boolean without value)
• Support for shorthands (e.g.: --test can also be called using -t)