Enhancement: "help-helpfile" config option for replacing !help nulla…

…ry-arg helpfile

src/plugin/help.sjs

@@ -131,7 +131,7 @@ module.exports = {
             },
 
             help: {
-                help: [
+                help: client.config("help-helpfile") || [
                     "{{!}}help <query>",
                     " ",
                     "Display the help message for the topic located at the given query.",

src/test/plugin-help.sjs

@@ -40,6 +40,10 @@ const client = {
             return "@";
         }
 
+        if (value === "help-helpfile") {
+            return undefined;
+        }
+
         throw new Error(format("Error in testing: Plugin expects config value (%s) we don't have.", value));
     }
 };