Codechange: Let the compile generate the master command table out of templated command traits.

This is using a non-intrusive type-traits like templated system, which
allows compile-time validation that the command table and the command
enum match up.

src/town_cmd.cpp

@@ -48,6 +48,7 @@
 #include "object_base.h"
 #include "ai/ai.hpp"
 #include "game/game.hpp"
+#include "town_cmd.h"
 
 #include "table/strings.h"
 #include "table/town_land.h"