17397: Timeline Feature

This feature provides users with the ability to know what is going on by co-workers and customers.  It provides a timeline view of actions with ability to jump to the affected issues for more details.

I've done the TODOs, so feel free to start comment on the feature and the code.

![timeline2](https://cloud.githubusercontent.com/assets/6446/3143453/38e7cde2-e9fb-11e3-8fd8-89a9e466fdb5.png)
$this->timestamp ?