split common parts of AttributeRenderer into AbstractRenderer.  Add AdditionalRenderer (incomplete) for 'extra' fields in the form.
split common parts of AttributeRenderer into AbstractRenderer.  Add AdditionalRenderer (incomplete) for 'extra' fields in the form.

abourget/formalchemy-abourget,FormAlchemy/formalchemy,camptocamp/formalchemy,camptocamp/formalchemy,camptocamp/formalchemy,FormAlchemy/formalchemy,camptocamp/formalchemy,FormAlchemy/formalchemy,FormAlchemy/formalchemy