[core] render two levels 'values' parameter property with optgroup
[core] render two levels 'values' parameter property with optgroup

example:
$parameterSet=array(
  'feed'=>array(
     'name'=>'Feed',
     'type'=>'list',
     'values'=>array(
        'list A'=>array(
           'feed A1'=>'fA1',
           'feed A2'=>'fA2'
        ),
        'list B'=>array(
           'feed B1'=>'fB1',
           'feed B2'=>'fB2
        )
     )
  )
);

Signed-off-by: Pierre Mazière <de7336e35cef0f8a399cd781635c22e507b4a7ab@gmx.com>

LogMANOriginal/rss-bridge,RSS-Bridge/rss-bridge,simonbru/rss-bridge,ORelio/rss-bridge,GregThib/rss-bridge,mro/rss-bridge,kranack/rss-bridge,LogMANOriginal/rss-bridge,teromene/rss-bridge,simonbru/rss-bridge,Frenzie/rss-bridge,ORelio/rss-bridge,kranack/rss-bridge,ORelio/rss-bridge,kranack/rss-bridge,teromene/rss-bridge,kranack/rss-bridge,RSS-Bridge/rss-bridge,polo2ro/rss-bridge,Riduidel/rss-bridge,griffaurel/rss-bridge,mro/rss-bridge,sebsauvage/rss-bridge,Riduidel/rss-bridge,Riduidel/rss-bridge,RSS-Bridge/rss-bridge,Frenzie/rss-bridge