[Form] Moved the Validator component to the suggest section

There is no hard dependency to the Validator component.
Fixed constraint requirements for Doctrine Common
merged branch stof/composer_deps (PR #3553)

Commits
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f26c1ce Fixed constraint requirements for Doctrine Common
011791d [Form] Moved the Validator component to the suggest section

Discussion
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Composer deps

There is no hard dependency to the Validator component in the Form, as said on Twitter when @harikt tried to use it. I kept the Locale component as a requirement as it is used by the LanguageTyep, CountryType and LocaleType which will be registered when using the CoreExtension.

The constraints for Doctrine deps are fixed too: adding an upper bound everywhere as we don't know the future to guarantee the compatibility (and for instance, 2.0.9 and lower were not compatible with ORM 2.2 as we had to fix the bundle), and the bridge is compatible with Common 2.2 too, not only with 2.1.

I found 2 other places where the dependencies should be discussed:

- the Validator component marks a hard dependency to Doctrine Common for its annotation reader. There is a dependency only when using annotation so it should not be a hard requirement IMO but a suggestion. the issue is that the [ValidatorFactory](https://github.com/symfony/symfony/blob/master/src/Symfony/Component/Validator/ValidatorFactory.php) (not used by the framework itself) will add an annotation loader when relying on the default value of the arguments, which means that people that don't take care will need Common. Would it make sense to change the default so that Common is needed only when the user explicitly asks to use annotations ? Moving Common from require to suggest would make it easier for people using the Validator component standalone if they don't use annotations
- the Security component suggests the Finder and ClassLoader components. But these ones are only used by the [dev script](https://github.com/symfony/symfony/blob/master/src/Symfony/Component/Security/Acl/Resources/bin/generateSql.php) used to generate the SQL schema shipped in the component. Does it really make sense to list them as people cloning the component should probably never use this script (which alters the files in the component) ?

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by fabpot at 2012-03-11T08:14:46Z

+1 for removing Doctrine Common as a required dependency for the Validator component.

+1 for removing ClassLoader and Finder from the Security suggestions.
[CssSelector] fixed CssSelector::toXPath() when the CSS selector is an empty string
fixed CS
Sets _format attribute only if it wasn't set previously by the user
added getNativeDefinition() to allow specifying an alternate InputDefinition for help generation
provided unmerged definition for correct help generation
merged branch meandmymonkey/xml-output-fix (PR #3569)

Commits
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705e460 provided unmerged definition for correct help generation
45bbb5b added getNativeDefinition() to allow specifying an alternate InputDefinition for help generation

Discussion
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[Console] Xml output fix

Bug fix: yes
Feature addition: no
Backwards compatibility break: no
Symfony2 tests pass: yes
Fixes the following tickets: #2667
Todo: add specific test

As per my comment [here](https://github.com/symfony/symfony/issues/2667#issuecomment-4431944), added the ability to provide an InputDefinition that will not be changed by merging with the Application InputDefinition..
merged branch iambrosi/issue2653 (PR #3564)

Commits
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aa53b88 Sets _format attribute only if it wasn't set previously by the user

Discussion
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Sets _format attribute only if it wasn't set previously by the user.

Fixes #2653