Make a small grammatical adjustment

The original form of the phrase - «The other option is to specifically
checking if a session has expired after the session is started.» - is
not entirely grammatically correct, as the infinitive form of «to check»
shall normally be used, or the gerund form, which is the form used in
this commit.
[Cookbook][External Parameters] Enhance description of environment variables
support Varnish in configuration blocks
Fixed broken external link to DemoController Test
bug #4292 Fixed broken external link to DemoController Test (danielsan)

This PR was submitted for the 2.5 branch but it was merged into the 2.3 branch instead (closes #4292).

Discussion
----------

Fixed broken external link to DemoController Test

Commits
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6cba2db Fixed broken external link to DemoController Test
[Cookbook][Doctrine] Fix typo in XML configuration for custom SQL function
bug #4297 [Cookbook][Doctrine] Fix typo in XML configuration for custom SQL functions (jdecool)

This PR was merged into the 2.3 branch.

Discussion
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[Cookbook][Doctrine] Fix typo in XML configuration for custom SQL functions

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

Commits
-------

2cb85a1 [Cookbook][Doctrine] Fix typo in XML configuration for custom SQL function
routing example fixed with routing.xml file
minor #4298 Book HTTP Fundamentals routing example fixed with routing.xml file (peterkokot)

This PR was merged into the 2.3 branch.

Discussion
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Book HTTP Fundamentals routing example fixed with routing.xml file

Commits
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8c05dab routing example fixed with routing.xml file
Clarifying that the bundles best practices entry is for reusable bundles, not for app bundles
Some fixes thanks to @stof
minor #4250 Clarifying Bundle Best Practices is for *reusable* bundles (weaverryan)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #4250).

Discussion
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Clarifying Bundle Best Practices is for *reusable* bundles

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs? | No
| Applies to    | 2.3+
| Fixed tickets |

Hi guys!

I wanted to be a little bit more clear that the bundle best practices doc is all about structuring your reusable bundles, not necessarily your application bundles.

I realize I broke from the Cookbook-standard of "How to..." title, but this title sounded the best to me. I'm also not worried about breaking the anchor on the top title, since it's already the top of the page.

Thanks!

Commits
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1caa1fd Some fixes thanks to @stof
e7b1ae3 Clarifying that the bundles best practices entry is for reusable bundles, not for app bundles
Fix PropertyAccessorBuilder usage
bug #4300 [Components][PropertyAccess] Fix PropertyAccessorBuilder usage (Thierry Geindre)

This PR was merged into the 2.3 branch.

Discussion
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[Components][PropertyAccess] Fix PropertyAccessorBuilder usage

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.3, 2.4, 2.5
| Fixed tickets |

See https://github.com/symfony/PropertyAccess/blob/2.3/PropertyAccess.php

`getPropertyAccessorBuilder` does not exist. But the right fix might be to add the missing method.

Commits
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c0167da Fix PropertyAccessorBuilder usage
Changed to reference the correct twig template
minor #4302 View documentation had a reference to the wrong twig template (milan)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #4302).

Discussion
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View documentation had a reference to the wrong twig template

Just noticed this little discrepancy in the docs.

Commits
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d420491 Changed to reference the correct twig template
Fix spelling

"so-called" is a traditionally hyphenated compound word.
Improve readability
minor #4306 Improve readability (ifdattic)

This PR was merged into the 2.3 branch.

Discussion
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Improve readability

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.3
| Fixed tickets |

Commits
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a715baf Improve readability
minor #4287 support Varnish in configuration blocks (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
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support Varnish in configuration blocks

To be able to use them, fabpot/sphinx-php#20 has to be merged first. After that, the submodule reference has to be updated as well with this pull request.

@dbu @thierrymarianne Is Ruby the language to choose to get proper syntax highlighting?

Commits
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f2bf980 support Varnish in configuration blocks