[Protocol] Add tournament state event and tournament game commands

Adds the protocol layer for the tournament game mode:
- Event_TournamentState (2027) carrying phase, round counters, player
  standings, pairings, and settings (games_per_match)
- Command_ReportMatchResult / Command_AdvanceTournament /
  Command_TournamentSettingsSelect game command extensions (1037-1039)
- is_tournament flag on Command_CreateGame and ServerInfo_Game;
  is_tournament and parent_game_id on Event_GameStateChanged


Took 13 minutes

libcockatrice_protocol/libcockatrice/protocol/pb/game_commands.proto

@@ -180,6 +180,15 @@ message GameCommand {
         /// Server: Server_Player::cmdSetPlaymat
         /// Client: reflected via player properties changed event
         SET_PLAYMAT = 1035;
+
+        /// Report the result of a tournament match sub-game.
+        REPORT_MATCH_RESULT = 1037;
+
+        /// Advance the tournament to the next round.
+        ADVANCE_TOURNAMENT = 1038;
+
+        /// Select tournament settings.
+        TOURNAMENT_SETTINGS_SELECT = 1039;
     }
 
     extensions 100 to max;