fixed param converters
fixed param converters

Before this patch, if you defined a @ParamConverter annotation, it was not merged with
the automaticcally created @ParamConverter one (which means that you had 2 param converters
for the same parameter and only the first one was executed).

chalasr/SensioFrameworkExtraBundle,henrikbjorn/ParamConverter,sensiolabs/SensioFrameworkExtraBundle,xabbuh/SensioFrameworkExtraBundle,chalasr/SensioFrameworkExtraBundle,stof/SensioFrameworkExtraBundle