Improve Bamboo EC2 docs

Feedback from a customer:

"The problem I had was to grasp the concept of elastic builds. I attached an image which I made to simplify the concept, not sure if I understood correct. The whole artifact part is unclear to me and the documentation doesn't goes into this. So a bamboo plan is triggered, starts up an elastic instance and that instance will checkout the code and run the maven command. This will result in a couple of artifacts (jar files, reports) will those artifact be available on my bamboo server or are they 'lost' on the elastic instance?
The rest of the 'unclear part' was manly my lack of knowledge about EC2 and the possibilities, reading up on this helped understanding the whole concept and setting up."