title: How to add group level action/events button in ng-grid
body: <p>I have some data , which will be displayed in ng-grid groupwise. For some of the groups i need to provide some actions like.</p>
  
  <p>1) save particular group data    [Save button] </p>
  
  <p>2) Do some opertions with that group data [ Test Button].</p>
  
  <p>I tried in google search but not find any releate information.
  How can we do this ?</p>