Add docs about trait's requirement.
Remove PHPOption support from ParamConverter

The PHPOption support was added because of my custom EntityReopsitory which returns PhpOption objects from it's find method.
This was done in error as it breaks the EntityRepository's interface.
Merge branch 'develop' into scrutinizer-issue-fixes

Conflicts:
	src/Axstrad/Bundle/ExtraFrameworkBundle/Request/ParamConverter/DoctrineParamConverter.php