[FrameworkBundle] Add Event Dispatcher debug command
[Twig][Form] Moved configuration key twig.form.resources to
twig.form_themes
[Validator] Add ClassMetadata plural methods for convinience
feature #11917 [Validator] Add ClassMetadata plural methods for convinience (jakzal)

This PR was squashed before being merged into the 2.6-dev branch (closes #11917).

Discussion
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[Validator] Add ClassMetadata plural methods for convinience

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #4143
| License       | MIT
| Doc PR        | -

I realised there's no specific place to document this methods, as the code examples always include all the formats. I think it's enough if IDE autocompletes these methods.

Commits
-------

0fd6769 [Validator] Add ClassMetadata plural methods for convinience
feature #11343 [Twig][Form] Moved twig.form.resources to a higher level (stefanosala)

This PR was merged into the 2.6-dev branch.

Discussion
----------

[Twig][Form] Moved twig.form.resources to a higher level

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | #11296
| License       | MIT
| Doc PR        | https://github.com/symfony/symfony-docs/pull/4003

Commits
-------

ab0b5e6 [Twig][Form] Moved configuration key twig.form.resources to twig.form_themes
feature #10388 [FrameworkBundle] [Command] Event Dispatcher Debug - Display registered listeners (matthieuauger)

This PR was merged into the 2.6-dev branch.

Discussion
----------

[FrameworkBundle] [Command] Event Dispatcher Debug - Display registered listeners

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT

------------------------------------------
[Update] The PR has been updated in order to comply with @stof comments.

Current status :
- [x] New event dispatcher Descriptor
- [x] Manage all callables
- [x] Unit tests
- [x] Text description
- [x] XML description
- [x] Json description
- [x] Markdown description

-----------------------------------------
Hi. In some big applications with lots of events, it's often hard to debug which classes listen to which events, and what is the order of theses listeners. This PR allows to run

- *event-dispatcher:debug* which displays all configured listeners + the events they listen to

![capture d cran de 2014-03-07 20 13 56](https://f.cloud.github.com/assets/1172099/2361104/40a86a62-a62d-11e3-9ccd-360a8d75b2a4.png)

- *event-dispatcher:debug* **event** which displays configured listeners for this specific event (order by priority desc)

![capture d cran de 2014-03-07 20 14 31](https://f.cloud.github.com/assets/1172099/2361100/31e0d12c-a62d-11e3-963b-87623d05642c.png)

The output is similar to *container:debug* command and is available in all supported formats (txt, xml, json and markdown).

I found another PR with same goal (#8234), but the approach looks too complicated to me plus I think we should fetch the listeners directly with the event_dispatcher.

Commits
-------

ce53c8a [FrameworkBundle] Add Event Dispatcher debug command
[Debug] Symfony debug extension
[Debug] a README for the debug extension
[VarDumper] algo to clone any PHP variable to a breadth-first queue
[VarDumper] symfony_debug ext. fast and memory efficient cloning algo
[VarDumper] add casters for per class/resource custom state extraction
[VarDumper] casters for exceptions representation
[VarDumper] casters for SPL data structures
[VarDumper] casters for PDO related objects
[VarDumper] casters for Doctrine objects
[VarDumper] casters for DOM objects
[VarDumper] interface for dumping collected variables
[VarDumper] CLI dedicated dumper and related abstract
[VarDumper] HTML variant of the CLI dumper
[VarDumper] spec for json based representation of PHP vars