enhance the pk handling to use the real PK name and not only 'id',
fix new sensioFrameworkBundle 2.1 requirement:
ParamConverterInterface::apply() method now must return a Boolean value indicating if a conversion was done
Currently, parameters like "author_slug" are translated by the param
converter to a "->filterByAuthor_slug()" call. I changed this behavior
and they are now translated to "->filterByAuthorSlug()".
