Initial validation chapter import

[weaverryan]

Hey guys-

This is the refactoring of the validation guides into one official book chapter. Some pieces were moved into the cookbook and others into the reference section. There are also random formatting fixes.

What I'm really looking for is any feedback on the validation chapter itself. It's not complete (e.g. validation groups aren't covered), but we'll merge this in as a start.

Thanks!

[weaverryan]

Also, this will break a link on the following page: http://symfony.com/doc/2.0/

The Validation link will now need to be /doc/2.0/book/validator.html

[fabpot]

"by another" ("a" should be removed)

[fabpot]

I like this chapter very much. It's easy to read, simple, and concise. Great job Ryan!

[weaverryan]

Fabien-

Thanks for the feedback :) - I've made all of the fixes you've noted. I've also added the following to our running spreadsheet of documentation todos (which I'll plan to move into Jira when we get that far):

• Add section about Doctrine+Validation
• Add cookbook about Choice + callback and also Doctrine choice (link to from chapter)
• Add note on validating an array

I'll merge this in now - I've got everything fixed or noted.

Thanks!