squash #6156 (#6161)

* move common server files

* update includes with move

* create participant, move code

* fix linker errors

* fix regressions

* mark function as override to make clang happy

* split out spectator to new file

* forgot to add to cmakelists

* autocompleter picking wrong casing for var name

* clean up forwards declarations in player

* fix includes in game

common/server/game/server_spectator.h

@@ -0,0 +1,17 @@
+#ifndef SPECTATOR_H
+#define SPECTATOR_H
+
+#include "server_abstract_participant.h"
+
+class Server_Spectator : public Server_AbstractParticipant
+{
+    Q_OBJECT
+public:
+    Server_Spectator(Server_Game *_game,
+                     int _playerId,
+                     const ServerInfo_User &_userInfo,
+                     bool _judge,
+                     Server_AbstractUserInterface *_handler);
+};
+
+#endif