Added an option to disable Locale listener

[romaricdrigon]

Hi,

In some case, using the Symfony2 locale (for example from the Request) to automatically filter entities using the Translatable extension can lead to unwanted results. I came across such case in an application where the locale was already managed explicitly.

In this PR, we create an optional disable_locale_listener option. The default value is true, so there are no BC break.

Q	A
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?	no
Tests pass?	~
Fixed tickets	~
License	MIT
Doc PR	Doc written

[stof]

@romaricdrigon are you still interested in this feature ? If yes, please update it based on the feedback I gave you previously, and please rebase it to fix conflicts

[tyx]

I can continue the work if needed. I definitively need this feature

[romaricdrigon]

I was not sure anyone but me was needing that one. Sure I will work on it.

[shouze]

Definitely a must have :+1:

[romaricdrigon]

Hi all, I've just updated my code with your feedback @stof , and squashed my commits.

[shouze]

Oh yeah! can't wait!

[Pierstoval]

Ping @stof : this can be merged IMO ?