Added notes specifying the propagation behaviour for kernel.view and kernel.exception.
Add missing info about kernel.request event.
Changed phrasing to explain the effects off propagation stopping.
Fix incorrect event name.
Updated installation instructions to use the new Symfony Installer
Removing some installation instructions
update contribution guide for 2.7/3.0
Restored the original section title
Minor grammar fix
Fixed section headers
Fixed some code indentation
Fix indentation of YAML example
Linked the PDO/DBAL Session article from the Doctrine category
minor #4649 Linked the PDO/DBAL Session article from the Doctrine category (javiereguiluz)

This PR was squashed before being merged into the 2.3 branch (closes #4649).

Discussion
----------

Linked the PDO/DBAL Session article from the Doctrine category

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | #4416

Commits
-------

cb4784a Linked the PDO/DBAL Session article from the Doctrine category
replace Symfony2 with Symfony
minor #4652 replace Symfony2 with Symfony (xabbuh)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #4652).

Discussion
----------

replace Symfony2 with Symfony

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

Commits
-------

224c283 replace Symfony2 with Symfony
minor #4659 Fixed some code indentation (javiereguiluz)

This PR was merged into the 2.3 branch.

Discussion
----------

Fixed some code indentation

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

Commits
-------

0b7cb0e Fixed some code indentation
Update the_controller.rst

Corrected error in the sample code.
bug #4646 Update the_controller.rst (teggen)

This PR was submitted for the 2.6 branch but it was merged into the 2.3 branch instead (closes #4646).

Discussion
----------

Update the_controller.rst

Corrected error in the sample code.

Commits
-------

40e63b9 Update the_controller.rst
minor #4660 Fix indentation of YAML example (xelaris)

This PR was merged into the 2.3 branch.

Discussion
----------

Fix indentation of YAML example

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

Commits
-------

52a05c3 Fix indentation of YAML example