[FIX] website_slides: allow creating partner when adding attendee

How to reproduce:
1. Go to any course
2. Click on the button 'Add attendees'
3. Type the recipients name 

"Create and edit ..." should be displayed but is not.

To reenable this feature, we remove the option no_create_edit on partner_ids
of the slide_channel_invite_view_form form to enable the creation of partner
when adding attendee to a course.

As the support for the force_email context has been discontinued, we don't
reenable the quick_create as it can create partner without email (if the user
enter a non-valid email). But we reenable the "create edit" option with a view
that force the user to enter an email: base.view_partner_simple_form (like
done on some views in odoo/odoo#149806).

Task-3868824

closes odoo/odoo#162190

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

addons/website_slides/wizard/slide_channel_invite_views.xml

@@ -24,8 +24,8 @@
                                     widget="many2many_tags_email"
                                     placeholder="Add contacts..."
                                     required="send_email"
-                                    options="{'no_create_edit': True, 'no_quick_create': True}"
-                                    context="{'show_email': True}"/>
+                                    options="{'no_quick_create': True}"
+                                    context="{'show_email': True, 'form_view_ref': 'base.view_partner_simple_form'}"/>
                             </group>
                             <group col="2" invisible="not send_email">
                                 <field name="lang" invisible="1"/>