[MIGRATE] website_forum: migration to the new API, cleaning and linting of models and controllers.

Main cleaning
- remove introduction_message, introduced in saas-6 with inboung forum, that was quite
a duplicate of description.
- renamed relevancy_option_first and relevancy_option_second, introduced in saas-4
with inbound forum
- renamed type of post to post_type to avoid confusion with the type keyword
- some cleaning in templates
[FIX] Website_quote: Fixed history and quotation name in left sidebar menu, fixed usability issues in preview quotation button,[IMP] Improved update quote button when quotation is accepted it will display back to sale order button, updated Edit Template link.