STAR conference (stcon) module

• It is composed of three parts: a) conference b) session c) talk, so it's actually three modules in one (three node types)

• ACL for talks: usually, pwg convener creates agenda, so she is the one who actually adds sessions and talks - it is allowed by "create talk" permission. Users usually have "edit talks" permission, because they need to upload files and fill in abstracts for their talks.