[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
Adder and remover sidenote

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | none

There are cases when you only want either adder or remover, important to know both of them need to be found if any is to work.
Merging emphasized notes

Merged both notes into one, in accordance to discussion feedback.
intro the var-dumper component
review effect
Reduce line length
doc for Dumpers
split intro/advanced sections
use VarCloner instead of Php/ExtCloner
add sidebar for the built-in server in VMs
Reworded a misleading Doctrine explanation
fix route prefix in PHP code example
move Dumper section above the Caster one
Remove incoherence between Doctrine and Propel introduction paragraphs
Update form_customization.rst

In the Form chapter of Book for Symphony 2.3, we use '{{ form(form) }}' to render the entire form ( in contrast to '{{ form_widget(form) }}' for older version of Symfony ). so maybe it should use '{{ form(form) }}' here for consistency.
Fixed typo
[reference][configuration][security]Added key_length for pbkdf2 encoder
Tweaks after proofreading the 2.6 OptionsResolver stuff
Also did a quick proofread