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/economy.cpp

@@ -48,6 +48,7 @@
 #include "goal_base.h"
 #include "story_base.h"
 #include "linkgraph/refresh.h"
+#include "economy_cmd.h"
 
 #include "table/strings.h"
 #include "table/pricebase.h"