[2.3] Examples that points to the DataCollectorListener should be removed.
Removed outdated translations from the official list
Fix documentation for group_sequence_provider
document multiple recipients in XML configs

Adds an example on how to configure multiple recipients in Monolog
for sending log entries as e-mails.
[Reference] fix namespace in Expression constraint
tweaks for the web server configuration chapter
Fixed minor typos.
Removing extra whitespace
bug #4153 [Reference] fix namespace in Expression constraint (xabbuh)

This PR was merged into the 2.4 branch.

Discussion
----------

[Reference] fix namespace in Expression constraint

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.4+
| Fixed tickets |

Commits
-------

1deabde [Reference] fix namespace in Expression constraint
feature #4142 [Cookbook][Configuration] tweaks for the web server configuration chapter (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
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[Cookbook][Configuration] tweaks for the web server configuration chapter

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes
| Applies to    | all
| Fixed tickets |

Tweaks to #3915 as suggested by @weaverryan.

Commits
-------

93bbd14 tweaks for the web server configuration chapter
Added the schema_filter option to the reference
feature #4150 Added the schema_filter option to the reference (peterrehm)

This PR was submitted for the 2.5 branch but it was merged into the 2.3 branch instead (closes #4150).

Discussion
----------

Added the schema_filter option to the reference

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | ?
| Fixed tickets | -

Shall the optional setting be added to XML as well? How?
I am unsure if it is actually to which version this relates to the DoctrineBundle.

Relates to doctrine/migrations#101

Commits
-------

20cba4e Added the schema_filter option to the reference
Merge branch '2.3' into 2.4

* 2.3:
  Added the schema_filter option to the reference
  Removing extra whitespace
  tweaks for the web server configuration chapter
Added custom format page to translation component
Link from introduction section
Small fixes
Cleanups
Fixed version for composer install
Improvements based on comments
Extra improvements based on comments