[ADD] website_theme_install: try to make theme multi website compliant

From now, when you install a theme, it load the data from xml to template
table theme [ir.ui.view|ir.attachment|website.page|website.menu].

Data are only copied from this template table into the real table when you
choose a theme on a website; Making them website_specific and with a link
to the original to allow futur update.

A special case is done to create theme.ir.ui.view when you are installing
a theme, even if you continue to use template tag to create quick view.

Co-authored-by: Derie Romain <rde@odoo.com>
Co-authored-by: Kersten Jérémy <jke@odoo.com>