symfony/symfony-docs — pull request #1797 by greg0ire (2012-10-08 15:12:08+00:00)
Title: Document the prototype name of the Collection Type

I wanted to answer [this nasty-looking question](http://stackoverflow.com/questions/12782911/symfony2-prototype-contains-not-needed-field/12783415), when I found this interesting option in the code. It is not documented, and I don't know why, so here is a PR for what could be a minimal, to-be-improved documentation for this feature.

This feature seems to be 2.1-only, so do NOT merge this in the 2.0 branch.