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
Improved naming
describe how to access form errors
[Form] document $deep and $flatten of getErrors()
use the C lexer for Varnish config examples
Completely re-reading the controller chapter
Added the release dates for the upcoming Symfony 3 versions
Removed unnecessary use statement in code example in the debugging cookbook
moved inlined URL to the bottom of the file
tweaks to the Twig reference
refer to the VarDumper component for dump()
Fixed make file
Bot fixes
minor #4448 [Book][HTTP Cache] moved inlined URL to the bottom of the file (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
----------

[Book][HTTP Cache] moved inlined URL to the bottom of the file

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

Commits
-------

28137ab moved inlined URL to the bottom of the file
Update doctrine.rst