Initialize project with Apache CLI Library

[averageandyyy]

• Created prelimnary classes such as Ui, Parser, Author and Tantou to try out CLI Library
• Try add -a andy to see andy being echoed
• add and add -b andy are invalid and will simply result in a greeting message
• Consider removing abstract AddCommand class
  • Idea was that all downstream Add-related commands would inherit, but a simple check to generate the relevant class might be more straightforward
• getAuthorCommand and isValidAuthorCommand definitely have overlap, to improve implementation but i think the general idea seems sound