Linkify hostname/port combos in task list

A common use case for task lists is finding the hostname and random port
assigned to a given task. Linkify them where possible. For multiple
ports, linkify the port numbers.

* Use same font color for hover/focus link states as `.btn-primary`.
* Move host/port formatting from model to component because it creates
  anchors specific to TaskListItemComponent.
Make `<th>` wrapping checkbox clickable

This mimics behavior of the rows below: click the checkbox or the
wrapping table cell.
Merge pull request #316 from mesosphere/linkify-task-hostname-port

Linkify hostname/port combos in task list