devtools: change shortcuts for switching prompts

As requested in #9 changed from PageUp/PageDown to CTRL+,/CTRL+.(close #9)
Later I want to add Dirac welcome console message which will explain
keyboard shortcuts to new users.

resources/unpacked/devtools/front_end/console/ConsoleView.js

@@ -1059,8 +1059,8 @@ WebInspector.ConsoleView.prototype = {
 
         if (dirac.hasREPL) {
             keys = [
-                shortcut.makeDescriptor(shortcut.Keys.PageDown),
-                shortcut.makeDescriptor(shortcut.Keys.PageUp)
+                shortcut.makeDescriptor(shortcut.Keys.Comma, WebInspector.KeyboardShortcut.Modifiers.Ctrl),
+                shortcut.makeDescriptor(shortcut.Keys.Period, WebInspector.KeyboardShortcut.Modifiers.Ctrl)
             ];
             this._shortcuts[keys[0].key] = this._selectNextPrompt.bind(this);
             this._shortcuts[keys[1].key] = this._selectPrevPrompt.bind(this);