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.
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.
Applied suggestion by Ryan
Update slash_in_parameter.rst

"name" in requirements is confusing, I had problem for doing the same and then after 2 days I found that the "name" should be same as the parameter, it is not part of symfony config

   requirements: 
        name: .+
Changed userName to username
describe how to access form errors
[Form] document $deep and $flatten of getErrors()
Removed unnecessary use statement in code example in the debugging cookbook
tweaks to the Twig reference
refer to the VarDumper component for dump()
Bot fixes
Fixed wrong indentation
remove versionadded directives for old versions
feature #4169 [Components][Form] document $deep and $flatten of getErrors() (xabbuh)

This PR was merged into the 2.5 branch.

Discussion
----------

[Components][Form] document $deep and $flatten of getErrors()

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes (symfony/symfony#9918)
| Applies to    | 2.5+
| Fixed tickets | #3660

This is based on #4168.

Commits
-------

0245e91 [Form] document $deep and $flatten of getErrors()
4221db8 describe how to access form errors
minor #4253 Adder and remover sidenote (kshishkin)

This PR was merged into the 2.3 branch.

Discussion
----------

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.

Commits
-------

59b932d Merging emphasized notes
bdd8325 Adder and remover sidenote
minor #4399 Explain form() and form_widget() in form customization (oopsFrogs, WouterJ)

This PR was merged into the 2.3 branch.

Discussion
----------

Explain form() and form_widget() in form customization

Continues https://github.com/symfony/symfony-docs/pull/4365

| Q   | A
| --- | ---
| Doc fix? | yes
| New docs? | no
| Applies to | all
| Fixed tickets | -

Original PR description:

> In the Form chapter of Book for Symfony 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.

Commits
-------

0086c5e Applied suggestion by Ryan
d653ff4 Update form_customization.rst
minor #4400 Continues #4307 (SamanShafigh, WouterJ)

This PR was merged into the 2.3 branch.

Discussion
----------

Continues #4307

Continues #4307

| Q   | A
| --- | ---
| Doc fix? | yes
| New docs? | no
| Applies to | all
| Fixed tickets | -

Original PR description:

 > "name" in requirements is confusing, I had problem for doing the same and then after 2 days I found that the "name" should be same as the parameter, it is not part of symfony config

Commits
-------

b412780 Changed userName to username
48f453d Update slash_in_parameter.rst
Added a reference to the Bootstrap 3 form theme
feature #4411 Added a reference to the Bootstrap 3 form theme (javiereguiluz)

This PR was submitted for the master branch but it was merged into the 2.6 branch instead (closes #4411).

Discussion
----------

Added a reference to the Bootstrap 3 form theme

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes
| Applies to    | 2.6+
| Fixed tickets | #4296

Commits
-------

c85a8ac Added a reference to the Bootstrap 3 form theme