Documented explicit namespace registration.
Added a note about removing the default namespace.
[#2979] Minor tweaks
document how to restrict a firewall to a specific host
[#2953][#2986] Tweaks to firewall hostname

Biggest change is to clarify that matching a firewall has no guarantee (is unrelated)
to whether or not access is restricted. Also, fixed up some of the regex.
Merge branch '2.3' into 2.4
Merge branch '2.4'

Conflicts:
	reference/dic_tags.rst
[#2986] Fix thanks to @WouterJ
[#2974] Fix thanks to @xabbuh
Update installation.rst
Merge pull request #3251 from bicpi/mini_fixes

Mini fixes
Merge pull request #3264 from bicpi/improve_method_description

[Components][OptionsResolver] Fix&improve replaceDefaults() description
Merge pull request #3265 from bicpi/fix_method_description

[Components][Console] Fix askConfirmation() description
Merge branch '2.2' into 2.3
Merge pull request #3271 from berny46/patch-1

Update Callback.rst
Merge pull request #3274 from bicpi/document_finish_request_event

[Components][HttpKernel] Add FINISH_REQUEST to events overview table
Updated required PHPUnit version

Running tests on version 3.6.4 ends with following error:

PHP Fatal error: Call to undefined method Symfony\Component\Form\Tests\SimpleFormTest::callback() in symfony/src/Symfony/Component/Form/Tests/SimpleFormTest.php on line 107
Merge branch 'issue-3162' of github.com:xabbuh/symfony-docs into xabbuh-issue-3162

Conflicts:
	contributing/code/tests.rst
fix code block indentation
Update composer installation command

The actual command have a reference to 2.3.* version