title: how to add custom tab inside shopping cart price rules
body: <p>I am trying to add a custom tab in magento backened Promotions/shopping cart price rules. What I need is when I choose any of rule, a custom tab shows below "Manage Coupons Code" and when I click on custom tab I must get a grid table with save and save and continue edit buttons. Can anyone suggest  me the right way to do this ? </p>
  
  <p>This is the window where I want to add new custom tab below "Manage Coupons Code":
  <img src="https://i.stack.imgur.com/Qo0Eb.jpg" alt="http://awesomescreenshot.com/0d34u825af"></p>