Update monolog.rst

Changed \n => &#xA; in xml example.
[Book] [Security] Fix typo
Refactored Doc Standards into its own file
Added heading level standard
Added hyperlink standard
Added formats standards
Merge pull request #2481 from WouterJ/doc_standards

Refactored Doc standards
[#2481] Tweaks to new docs standards doc
added assetic DIC tags
Merge pull request #2480 from pvolok/assetic_tags

Add assetic DIC tags reference.
[#2480] Tweaks to new Assetic DIC tags
Merge pull request #2488 from burci/bug-xml-newline

[cookbook][logging]Bug in xml monolog format example
Merge pull request #2490 from michaelperrin/bugfix/security-typo

[Book] [Security] Fix typo
Merge branch '2.0' into 2.1