Cleanup db

[Katrix]

• Add message table
• Add nullable message_id column to logged_actions
• Replace message stuff in notifications with message_id column
• Remove name in organization
• Replace comment in flags with message_id
• Replace message in project_log_entries with message_id
• Merge project_log_entries and project_log
• Replace comment in project_version_reviews with message_id
• Remove assets from project_versions. It's unused.
• Remove owner_name on projects.
• Replace notes on project with associative table between project and message_id.
• Replace username in user_session with user_id
• Run cleanup triggers a bit less often (every night)?
• Create a materialized view for the front page which is updated every x hours