[Form] DateTimeToRfc3339Transformer use proper transformation exteption in reverse transformation
[Form] Implemented support for buttons
[Form] Made submit buttons able to convey validation groups
[Form] Changed isset() to array_key_exists() to be consistent with ParameterBag
[Form] Fixed concatenation operator CS (see 7c47e34928c39e4797edc841423237a16588395e)
[Form] The option "validation_groups" can now be set to false to disable validation. This is identical to setting it to an empty array.
[Form] Fixed invalid use of FormException
[Form] Fixed incorrect doc comment
[Form] Removed deprecated code scheduled for removal in 2.3
[Form] Added leading backslashes to @exceptionMessage doc blocks
Merge branch '2.1' into 2.2

* 2.1:
  Fix default value handling for multi-value options
  [HttpKernel] truncate profiler token to 6 chars (see #7665)
  Disabled APC on Travis for PHP 5.5+ as it is not available
  [HttpFoundation] do not use server variable PATH_INFO because it is already decoded and thus symfony is fragile to double encoding of the path
  [Yaml] improved boolean naming ($notEOF -> !$EOF)
  [Yaml] fixed handling an empty value
  [Routing][XML Loader] Add a possibility to set a default value to null
  The /e modifier for preg_replace() is deprecated in PHP 5.5; replace with preg_replace_callback()
  [HttpFoundation] Fixed bug in key searching for NamespacedAttributeBag
  [Form] DateTimeToRfc3339Transformer use proper transformation exteption in reverse transformation
  Update PhpEngine.php
  [HttpFoundation] getClientIp is fixed.

Conflicts:
	.travis.yml
	src/Symfony/Component/Routing/Loader/XmlFileLoader.php
	src/Symfony/Component/Routing/Loader/schema/routing/routing-1.0.xsd
	src/Symfony/Component/Routing/Tests/Fixtures/validpattern.xml
	src/Symfony/Component/Routing/Tests/Loader/XmlFileLoaderTest.php
Merge branch '2.2'

* 2.2:
  Fix default value handling for multi-value options
  [HttpKernel] truncate profiler token to 6 chars (see #7665)
  Disabled APC on Travis for PHP 5.5+ as it is not available
  [HttpFoundation] do not use server variable PATH_INFO because it is already decoded and thus symfony is fragile to double encoding of the path
  Fix download over SSL using IE < 8 and binary file response
  [Console] Fix merging of application definition, fixes #7068, replaces #7158
  [HttpKernel] fixed the Kernel when the ClassLoader component is not available (closes #7406)
  fixed output of bag values
  [Yaml] improved boolean naming ($notEOF -> !$EOF)
  [Yaml] fixed handling an empty value
  [Routing][XML Loader] Add a possibility to set a default value to null
  [Console] fixed handling of "0" input on ask
  The /e modifier for preg_replace() is deprecated in PHP 5.5; replace with preg_replace_callback()
  fixed handling of "0" input on ask
  [HttpFoundation] Fixed bug in key searching for NamespacedAttributeBag
  [Form] DateTimeToRfc3339Transformer use proper transformation exteption in reverse transformation
  Update PhpEngine.php
  [PropertyAccess] Add objectives to pluralMap
  [Security] Removed unused var
  [HttpFoundation] getClientIp is fixed.

Conflicts:
	src/Symfony/Component/Console/Tests/Command/CommandTest.php
	src/Symfony/Component/Console/Tests/Input/ArgvInputTest.php
	src/Symfony/Component/HttpFoundation/Request.php
	src/Symfony/Component/HttpKernel/Kernel.php
merged branch bschussek/issue5383 (PR #6528)

This PR was merged into the master branch.

Discussion
----------

[2.3] [Form] Support buttons in forms

Bug fix: no
Feature addition: yes
Backwards compatibility break: yes
Symfony2 tests pass: yes
Fixes the following tickets: #5383
Todo: -
License of the code: MIT
Documentation PR: symfony/symfony-docs#2489

The general idea of this PR is to be able to add buttons to forms like so:

```php
$builder->add('clickme', 'submit');
```

You can then check in the controller whether the button was clicked:

```php
if ($form->get('clickme')->isClicked()) {
   // do stuff
}
```

Button-specific validation groups are also supported:

```php
$builder->add('clickme', 'submit', array(
    'validation_groups' => 'OnlyClickMe',
));
```

The validation group will then override the one defined in the form if that button is clicked.

This PR also introduces the disabling of form validation by passing the value `false` in the option `validation_groups`:

```php
$builder->add('clickme', 'submit', array(
    'validation_groups' => false,
));
```

The same can be achieved (already before this PR) by passing an empty array:
```php
$builder->add('clickme', 'submit', array(
    'validation_groups' => array(),
));
```

See the linked documentation for more information.

Commits
-------

faf8d7a [Form] Added upgrade information about setting "validation_groups" => false
d504732 [Form] Added leading backslashes to @exceptionMessage doc blocks
c8afa88 [Form] Removed deprecated code scheduled for removal in 2.3
36ca056 [Form] Simplified Twig code
ce29c70 [Form] Fixed incorrect doc comment
0bc7129 [Form] Fixed invalid use of FormException
600007b [Form] The option "validation_groups" can now be set to false to disable validation. This is identical to setting it to an empty array.
277d6df [Form] Fixed concatenation operator CS (see 7c47e34928c39e4797edc841423237a16588395e)
7b07925 [Form] Changed isset() to array_key_exists() to be consistent with ParameterBag
7b438a8 [Form] Made submit buttons able to convey validation groups
cc2118d [Form] Implemented support for buttons