DDC-1511: Suggestion on the docs for batch processing

[doctrinebot]

Jira issue originally created by user jamie0725:

I am refering to the examples on

http://www.doctrine-project.org/docs/orm/2.0/en/reference/batch-processing.html

Let's say you want to process a bulk of 25 objects and have a batchsize of 20.
With the code provided the last 5 would not be saved as far as I understand unless you do another flush after the for-loop.

This is probably very clear to any experienced Doctrine developer but maybe it is also confusing for beginners like me (some internet sources say, that flush is executed automatically at the end of the request, but obviously it is not). Maybe this could be mentioned somewhere?

[malukenho]

@Ocramius @lcobucci more documentation issue that can be closed.