[MonologBridge] Ignore empty context/extra by default in the ConsoleFormatter
[Form] Added "label_format" option
[Validator] Made it possible to store the cause of a constraint violation
[Intl] Integrated ICU data into Intl component
[Debug] add some file link format handling
[Debug] expose object_handle
updated CHANGELOG for 2.3.20
update CONTRIBUTORS for 2.3.20
updated VERSION for 2.3.20
bumped Symfony version to 2.3.21
updated CHANGELOG for 2.5.5
updated VERSION for 2.5.5
[DependencyInjection] Removed unreachable code
bumped Symfony version to 2.5.6
[Validator] Update validators.zh_CN.xlf, fix translation error
minor #12070 [Validator] Update validators.zh_CN.xlf, fix translation error (michaeljayt)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #12070).

Discussion
----------

[Validator] Update validators.zh_CN.xlf, fix translation error

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

Commits
-------

ab5aaab [Validator] Update validators.zh_CN.xlf, fix translation error
[DX] Moved constants to a final class
minor #12074 [DX] Moved Security constants to a final class instead of a long named interface (iltar)

This PR was merged into the 2.6-dev branch.

Discussion
----------

[DX] Moved Security constants to a final class instead of a long named interface

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | symfony/symfony-docs#4188

This PR is based on feedback from the documentation repository. The DX suggestion was to rename the new `SecuritySessionStorageInterface` to `Security`. This would make it easier to use the constants before 2.6 is released. In this PR I have also update all usages of this constant because an open PR is now merged which used those constants.

List of changes:
 - SecurityBundle, usage of constants
 - Security Component (core & http), usage of constants
 - Tests, usage of constants
 - Added a test to verify the sync from `Security` to `SecurityContextInterface` for BC purposes

Commits
-------

b23084a [DX] Moved constants to a final class
minor #12072 [DependencyInjection] Removed unreachable code (unkind)

This PR was merged into the 2.6-dev branch.

Discussion
----------

[DependencyInjection] Removed unreachable code

| Q             | A
| ------------- | ---
| Bug fix?      | not really
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

According to undefined $e, this is an unreachable code. As I can see, circular references are handled by parent method.

Commits
-------

ecedea2 [DependencyInjection] Removed unreachable code
remove invalid tests

With #12046, the `getLocale()` method isn't overriden anymore by the
`Translator` from the FrameworkBundle, but the locale is set by the
new `TranslatorListener`. Therefore, the tests ensuring the old
behavior are removed.