Download feature is added into asset menu item

Download as csv was not getting rendered on the asset type list page and the usability is also getting suffered due to the position of the link. Hence moving the link to menu for better availability. 

![download-as-csv](https://f.cloud.github.com/assets/6417646/2407437/39058f3e-aa8c-11e3-8fe6-73f8d91dae71.png)