[CSM] Client side modding

* rename GameScripting to ServerScripting
* Make getBuiltinLuaPath static serverside
* Add on_shutdown callback
* Add on_receiving_chat_message & on_sending_chat_message callbacks
* ScriptApiBase: use IGameDef instead of Server
  This permits to share common attribute between client & server
* Enable mod security in client side modding without conditions

src/content_abm.cpp

@@ -26,7 +26,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "settings.h"
 #include "mapblock.h" // For getNodeBlockPos
 #include "map.h"
-#include "scripting_game.h"
+#include "serverscripting.h"
 #include "log.h"
 
 void add_legacy_abms(ServerEnvironment *env, INodeDefManager *nodedef) {