'X' and 'O' now globally referred to as icon.
Remove View dependency from InputValidator.
Extract tests from AI class, improve test coverage.
Reorganize directory structure to follow convention.
Extract view logic from InputValidator.
Fix require paths.
Naming: globally revise "input" to "move".
Naming: globally revise "space" to "cell".
Replace struct with Player superclass for more idiomatic initialization.
Improve distinction between game and board. DRY