[MIGRATED] website_forum: migrated website_forum into new api + solved s...

...ome bugs

[IMP] website_forum: removed unnecessary imports
[IMP] website_forum: improved badges access for anonymous user
[IMP] wesite_forum: bug solved for ckeditor

- Task: https://www.odoo.com/web?&debug=#id=9031&view_type=form&model=project.task
- Pad: https://pad.odoo.com/p/r.4HSUoPQ9tBfdQEdN
After discussing with @fpodoo , last news for this point:
- indeed karma_* fields are not necessary (they are basically related fields), remove them (replace them by post.forum_id.karma_*, this should not be too verbose now that we can use the new API for the rest of the computation); you will have to update the forum views accordingly
- keep can_* (because there is logic in them)
- keep the karma system as it is, moving to a badge-based configuration is not a priority