* book borrowing, lending and returning
* event creation
* "sticky" news flag
* songs
* news editor for administrators
* PDF header fix
* draft flag for Document and Article: only writer and administrators see it
    from the Document/Article list, in preview mode
* full Document/Article list for administrators
* polls
* chat
* Users' favourite forum topics
* article categories
* blog
* site-based theme for ckeditor (both ui and the editor)

Song
    id
    title
    createdBy
    createdAt
    SongVersion[]
        id
        createdBy
        createdAt
        content

News
    lead

Poll
    id
    createdAt
    createdBy
    updatedAt
    updatedBy
    updateReason
    endTime (timestamp/date?)
    anyoneCanAddAnswers
    question
    multiselect
    voters
    PollAnswer[]
        id
        createdAt
        createdBy
        updatedAt
        updatedBy
        updateReason
        voters
        text

UserForumViewed
    User
    ForumTopic
    timestamp of last visit

BlogPost
    id
    title
    slug
    timestamp
    lead (?)
    text
    poster
    public

ForumTopicGroup
    visible
    locked

ForumTopic
    roles who can access it
    visible
    locked

ForumPost
    last edited by
    last edited timestamp
    last edit reason
    edit count

Event
    last edited by
    last edited timestamp
    last edit reason
    location
    commentable

PrivateChatMessage
    id
    from user
    to user
    timestamp

GroupChatMessage
    id
    from user
    to group
    timestamp

PublicChatMessage
    id
    from user
    to channel (ChatChannel class with id and name fields)
    timestamp