FOFModel save with FOFForm and fieldsets

Hi Nic,

I'm saving articles based on article.xml.

FOFForm works until it finds attribs/show_title.

In this case, FOFFormField has id=attribs_show_title.

When $form->getField is executed, it's returning no field with $form->getField('attribs_show_title');

So, the change submits $form->getField('show_title', 'attribs'); to get the right field.

Also, validateResult is initialized with true to avoid a warning.

Regards,
Anibal
Merge pull request #167 from anibalsanchez/patch-1

FOFModel save with FOFForm and fieldsets