message: Add simple dialog functionality to LUA
  Call using:
  ```lua
  client:simple_dialog("Test dialog")
  ```
diff: #include "MapClient.h"
  #include "Events/ChatMessage.h"
  +#include "Events/StandardDialogCmd.h"
  #include "Common/NetStructures/Entity.h"
  #include "Common/NetStructures/Contact.h"
  -
  +#define SOL_CHECK_ARGUMENTS
  #include <lua/lua.hpp>
  #include <sol2/sol.hpp>
  @@ -54,7 +55,11 @@ void ScriptingEngine::registerTypes()
  );
  m_private->m_lua.new_usertype<MapClient>( "MapClient",
  "new", sol::no_constructor, // The client links are not constructible from the script side.
  - "admin_chat_message", sendAdminMessage
  + "admin_chat_message", sendAdminMessage,
  + "simple_dialog", [](MapClient *cl,const char *dlgtext) {
  + auto n = new StandardDialogCmd(dlgtext);
  + cl->addCommandToSendNextUpdate(std::unique_ptr<StandardDialogCmd>(n));
  + }
  );
  }
  