store, control, wiki: repo access list reports effective access; one rule for outsiders !341

repo access list now folds owner, org admin, direct grant, team grant and org membership into one row per account with the highest role and its source ({user, role, source}), where before it listed direct grants only. ListAccess had no other caller and goes.

Outsiders get one rule for an org: existence and members are public, teams are for members, and a non-member asking for teams is refused (exit 4) rather than told the org does not exist. Users page says so. Store unit test and an e2e covering both.

Closes #200