Added lables for youngest and oldest instances in instances view

The labels are added to make it easy to find the oldest or youngest
instance for a role at a glance.  This is especially useful when
deciding which instances to terminate or which ones to check for
latest updates.

![image](https://cloud.githubusercontent.com/assets/7783905/3248306/6cf0b2ea-f18d-11e3-80ed-67bd9c688cff.png)