[FIX] web, website: display default company name on frontend layout

Before, the "Company name" placeholder was hardcoded in the frontend
layout template, and the user had to change it with his company name
from the website view, which was not user-friendly if the website module
was not installed.

Now, by default, the frontend layout template displays the user's
company name. If the website module is installed, it is editable.

task-2468472

closes odoo/odoo#69943

Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>