[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
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.
[DebugBundle] fix dev dependencies