Add tutorial mode

[acrosman]

Each game needs a tutorial mode for new players. The tutorial should be a guided walk through of how to play the game. It should include overlay text to tell the player what to expect, show a sample round of the game, and then tell them which control to use after the round.

Each tutorial should follow the same pattern:

1. Players who haven't seen the tutorial should be offered the chance to see the tutorial.

• Once a player sees the walk through a status flag must be set in the player's saved game file.
• Players who have seen the tutorial should be able to select a replay from the instructions screen.

2. The player should see an overlay explaining what the game does in each round, with a next button.
3. The overlay should disappear after the next button is clicked, and the game should display at the game's lowest setting.
4. The play should see an indicator of where they should click, or otherwise interact with the game to complete that round.
5. The tutorial should offer to complete a second round.

• If the player selects they want to continue the tutorial should show them a second round.
• After the second round, or if the player skips the second round, the tutorial ends.

6. The game should then begin it's main game, and save that the player has seen the tutorial.