Prep apps for app store

[kronosapiens]

See checklist here: https://api.slack.com/start/distributing/guidelines

• [x] Remove @channel from messages
• [x] Automatically add bots to log-channel when set
• [x] Remove messaging functionality for apps, put ephemeral messages in log channel
• [x] Audit error messages
• [x] Add help messages to all slash commands
• [ ] #60
• [x] Add explanations for different scopes

[kronosapiens]

Chores submission: https://app.slack.com/app-settings/T0103CT3AEB/A0105GJRN4T/submitted