[WCM] Skip console commands from event listeners

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes (symfony/symfony#9235)
| Applies to    | master
| Fixed tickets | none
[Translation] added method to expose collected message
[OptionsResolver] Adjusted the OptionsResolver documentation to describe the 2.6 API
Added missing mailer class and use statements
Removed duplicate use statements
intro the var-dumper component
review effect
Reduce line length
doc for Dumpers
split intro/advanced sections
Merge pull request #1 from peterrehm/patch-9

Added mailer class and use statements
use VarCloner instead of Php/ExtCloner
first import of the "Official Best Practices" book
Fixed some technical problems as suggested by Wouter
Added an index directive to the first chapter
updated fabpot/sphinx-php module reference
added the missing "best-practice" directive import in Sphinx configuration
Renamed "official best practices" to "best practices"
Fixed some typos reported by @henrikbjorn
Added config example for Varnish 4.0