Add cheat and console command to set game date.

Run "date" command on cmdline to set date.

Ex:
$ date 0004 06 13
sets date to June 13th, year 4

src/openrct2/interface/Console.cpp

@@ -1407,6 +1407,7 @@ static const console_command console_command_table[] = {
     { "remove_unused_objects", cc_remove_unused_objects, "Removes all the unused objects from the object selection.", "remove_unused_objects" },
     { "remove_park_fences", cc_remove_park_fences, "Removes all park fences from the surface", "remove_park_fences"},
     { "show_limits", cc_show_limits, "Shows the map data counts and limits.", "show_limits" },
+    { "date", cmdline_for_date, "Sets the date to a given date. Format YYYY MM DD, YYYY MM, or YYYY."}
 };
 
 static sint32 cc_windows(const utf8 **argv, sint32 argc) {