Merge pull request #1 from AbrarSyed/master

Uber Gradle revamp
DisplaySystem; ConsoleGui (encapsulates Blacken code)

- Added DisplaySystem
- Simplified System; it's just an interface now
- Added ConsoleGui to encapsulate/abstract the GUI code
Resolve #4: Gui interface

- Added GUI interface
- Migrated all code to use that instead
- Game creates the main (Console) GUI
Screen tests; clean up imports.
Arena Screen tests (simple, but it's still something).