Do like other enterprise modules in Odoo and display missing main applications
from enterprise in community: social and knowledge.

SPECIFICATIONS

Create `ir.module.module` records for knowledge, social and appointment apps
in Odoo Community, so that users searching for those apps can see them in the
correct category with the correct icon. They can then be redirected to Odoo
website for more information about the module or an upgrade plan to use the
enterprise version.

Knowledge
  * create the record
  * use the module_category_productivity category

Appointment
  * update the record to use the new icon
  * use the module_category_marketing category (instead of sales)

Social
  * create the record
  * use the module_category_marketing category

Task-3054412

closes odoo/odoo#103324

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