Move 'helpfile' definition to the Help module.

common/content/dactyl.js

@@ -1403,10 +1403,6 @@ var Dactyl = Module("dactyl", XPCOM(Ci.nsISupportsWeakReference, ModuleBase), {
                         groups.every(function (g) !g.validator || g.validator(val))
             });
 
-        options.add(["helpfile", "hf"],
-            "Name of the main help file",
-            "string", "intro");
-
         options.add(["loadplugins", "lpl"],
             "A regexp list that defines which plugins are loaded at startup and via :loadplugins",
             "regexplist", "'\\.(js|" + config.fileExtension + ")$'");

common/modules/help.jsm

@@ -445,6 +445,13 @@ var Help = Module("Help", {
     javascript: function initJavascript(dactyl, modules, window) {
         modules.JavaScript.setCompleter([modules.help.exportHelp],
             [function (context, args) overlay.activeModules.completion.file(context)]);
+    },
+    options: function initOptions(dactyl, modules, window) {
+        const { options } = modules;
+
+        options.add(["helpfile", "hf"],
+            "Name of the main help file",
+            "string", "intro");
     }
 });