title: dropdown tab with split button dropdowns behavior
body: <p>I would like to use a dropdown tab, but a little bit tweaked: I would like to show a dropdown menu (without selecting the tab) when I press the caret, whereas if I press the tab voice or one of the drop menu items, the tab will be selected. </p>
  
  <p>Consider this: 
  <img src="https://i.stack.imgur.com/YaxC8.png" alt="enter image description here"></p>
  
  <p>if I press the down caret of "Dropdown", I would like to show the dropdown menu like this:
  <img src="https://i.stack.imgur.com/CIpml.png" alt="enter image description here"> </p>
  
  <p>and in case I select @fat or @mdo, the tab will be selected, <strong>otherwise it should be set back to its pristine version above</strong>. This is the actual behavior of a normal dropdown item in a tab, but <strong>the title opens the dropdown menu instead of opening a tab</strong>, and that's what I don't want. In other words, the tabs I could open would be three instead of two. So: how to differentiate the two components? </p>