Fix typo in DungeonMap

Went uncaught because the class file remained in my build folder
Game.rollDice is public
Expose Game.addMonster
Implement several Actions as classes
Use ExitAction in Game
Actions return a boolean
Action.execute returns if it was a valid action
Actions have descriptions, Client displays them
Forgotten InvestigateFountain test
Add remaining room feature investigation actions
Roll up the Game.action loop
Fix death message typo