Add clusterssh recipe

Adds clusterssh for Mac and Linux platforms - *a tool to allow simultaneous control of multiple SSH sessions*.

Mac OS X installs [csshx](http://code.google.com/p/csshx/)
Other platforms should install the [clusterssh](http://sourceforge.net/apps/mediawiki/clusterssh/index.php?title=Main_Page) package

![csshX](https://f.cloud.github.com/assets/181548/125717/dcc60a40-6f1e-11e2-9155-7743ce204c57.png)