Add edit icon to action toolbar

The action toolbar should include an 'edit' icon.

Clicking on the edit button enables the user to change the original values they inputted when creating the item.

![screen shot 2014-09-18 at 1 44 31 pm](https://cloud.githubusercontent.com/assets/1521387/4319236/b6042fd6-3f29-11e4-9835-b19d52ea5b4d.png)



@andreit I think its a cool idea to reuse the modal for adding and editing. I mean more that we should try not duplicate this handling across all the component types (it means testing more things, and the possibility of more bugs if we were to introduce new components). I think we need some modal component that does all this handling for us. Something like

```javascript
modal()
  .path('/templates/channel_form_modal.html')
  .fields(['name', 'description'])
  .type(Channel)
  .edit(function() {
    // optional hook for when we edit something
  })
  .add(function() {
    // optional hook for when we add something
  })
```

That component can worry about if something is being edited or added, doing the scope refresh, etc.