Add sandbox rulebook.
Add generic "props" storage for scripts.
Allow scripts to trigger player finish.
Implement player init.
MainCharacters are now aware of their index.

This is so we don't need to pass the index along whenever we're passing
the PlayerPeer.
Add on_player_init event to rulebook.

This makes it cleaner to initialize each player.
Remove lap counter from MainCharacter.

The logic to track this is now in the rulebook.

Note: The HUD text is disabled until the modular HUD is in place.
Remove total laps from MainCharacter::New().
Merge branch 'master' into rulebook
Merge branch 'master' into rulebook
Add session.time to get the sim time.
Ignore property entries for now.
Fill out Session and Player help docs.
Fix typo.
Remove unused pSpeedFactor param.
Rename "on_player_init" to "on_player_joined".
Merge branch 'master' into rulebook
Remove factory functions.

Not necessary anymore.
Add initial HUD bits.
Add <array>.