Added dashboard and panel descriptions

I have added the functionality of add descriptions to the dashboards and the graph panels.

This is for the dashboard:

![image](https://cloud.githubusercontent.com/assets/8693668/5452287/6ed177c8-8519-11e4-8465-63d5aa5a9821.png)



And this one for each panel.


![image](https://cloud.githubusercontent.com/assets/8693668/5452265/31bcb8f2-8519-11e4-8cbe-728da3915c52.png)