Update monolog.rst

Changed \n => &#xA; in xml example.
[Book] [Security] Fix typo
Adding the mapped type to the form type references
[Reference][Forms] Fix options type for hours, minutes, seconds
[Reference][Forms] Fix typo introduced in previous commit
Added limitations in 'Managing Common Dependencies with Parent Services' with a caution
Updated contributor branch references - 2.0 no longer maintained

The current documentation refers throughout to making bugfix and
corrections against the 2.0 branch, however this is no longer
maintained. Updated with references to 2.1 to make this more
obvious to new contributors.
[Process] Update use of Process constants
Typo fixed
Improving Web server configuration
kernel.bundle_dirs doesn't exist in KernelParameters
Improved Luhn validator doc

Based on feedback from @WouterJ on the Iban validator doc.
See https://github.com/symfony/symfony-docs/pull/2521
Improved CardScheme validator doc

Based on feedback from @WouterJ on the Iban validator doc.
See https://github.com/symfony/symfony-docs/pull/2521
Fix code blocks in contributing/code/git.rst
Fix duplicated form widget
Changing translations examples to not use single character variable name
fix typo in auto_start
Fix custom Roles in entity_provider cookbook.

The documentation seems to assume the implementation present in commit
https://github.com/symfony/symfony/pull/1673, which reverted soon after due
to a potential, but undisclosed security hole (citation @schmittjoh in https://github.com/symfony/symfony/commit/af70ac8d777873c49347ac828a817a400006cbea).

This incorrect documentation has likely been the source of many
of the following issues:
* symfony/symfony#1538 - [ACL RoleSecurityIdentity] check if instance of Role
* symfony/symfony#1748 - Replace Role to RoleInterface for RoleSecurityIdentity
* symfony/symfony#4309 - Issue related to custom group (role) and ACL/ACE
* symfony/symfony#5026 - potential bug in Symfony\Component\Security\Acl\Domain\RoleSecurityIdentity
* symfony/symfony#5076 - [Acl] altered the behaviour of RoleSecurityIdentity
* symfony/symfony#5171 - Fix/role security identity
* symfony/symfony#5303 - [Security] Check for RoleInterface instead of Role object in RoleSecurityIdentity
* symfony/symfony#5909 - Allow Custom Roles to implement the RoleInterface
* symfony/symfony#6012 - Securityidentity fix
Refactored Doc Standards into its own file
Added heading level standard