Merge branch '2.1' into 2.2

Conflicts:
	contributing/documentation/standards.rst
Merge branch '2.2' into 2.3
Merge branch '2.3'
Merge pull request #3044 from WouterJ/document_expressionlanguage

[WIP] Add docs for ExpressionLanguage component
Fix HTTPS and Ajax notation
Include some updates after clarification
fix WSSE notation
Fixed namespace separator
[Cookbook][Session] Fix session proxy sample code
Update dic_tags.rst

  SwiftMailer plugin works only if its service defined with tag 'swiftmailer.default.plugin' and does not work with tag 'swiftmailer.plugin' specified in documentation
Update dic_tags.rst
Update dic_tags.rst
Updating the phrasing of a controversial sentence (in terms of grammar) thanks to my friend Ann

See https://github.com/symfony/symfony-docs/pull/3149/files#r7710566
Update dic_tags.rst
Merge branch 'component_names_consistency' of github.com:bicpi/symfony-docs into bicpi-component_names_consistency

Conflicts:
	book/translation.rst
Merge branch 'fix_proper_nouns_and_some_formatting' of github.com:bicpi/symfony-docs into bicpi-fix_proper_nouns_and_some_formatting

Conflicts:
	components/serializer.rst
	cookbook/form/unit_testing.rst
Fixing syntax error
add documentation for configuring additional monolog channels
fix typos, formatting, yaml code blocks
Minor fixes: Typos, Formatting, code, YAML code block