Opening a tab that already exists should visually make it "pop" to get user attention

[Col-E]

Steps

1. User opens class Dog and it appears in a new tab
2. User opens class Cat and it appears in a new tab
3. User opens class Dog and the TabPane containing both [Dog, Cat] switches to Dog, not opening a new instance of Dog
4. The border of the panel representing the Dog class should "pop" to get the user's attention

But what if a user wants to have Dog open twice?

I think having a right-click context menu on the tab title to duplicate the current display would be useful. This will be elaborated on in another issue: #5

[Col-E]

Done 05eb1c993b6453d8a66137c519d34ca7091c4912