Plug and play works beautifully for controllers!

Player quarter struct now changed to class,  all controllers handled
without error, char select screen also updates to reflect this
When 2 or more players are 'ready' in char select, they can progress to
game state with start button press, message displays when this is
possible
When controller is unplugged, it is closed as expected by input manager,
the player in char select is set back to 'not playing' state
When controller is plugged in, the message in the relevant players
screen changes from 'no controller connected' to 'press a to join'