Merge pull request #454 from symfony-fr/2.3

Merging 2.3 to 2.4
Merge pull request #455 from symfony-fr/2.4

Merging 2.4
fix typo
Missing translation for ParamConverter
Update use_virtuals_forms.rst

getDefaultOptions() method has been removed from FormTypeInterface in 2.3 and should be replaced by setDefaultOptions(OptionsResolverInterface $resolver). (information given in UPGRADE-2.1.md)
Merge branch 'jcrombez-patch-1' into 2.3
Merge branch 'cyrilchandelier-patch-1' into 2.3