Add teams for organisations

Organisations should be able to have teams.

Details

1. A team SHALL have a unique name within the organisation.
2. The requirements for the team name SHOULD be the same like for an organisation name.
3. A team SHALL have an optional description field.
4. The description field SHALL be constrained like the organisation description.
5. A team SHALL have a defined set of permissions for certain components:
   • repository
   • exec (edit settings)
   • read (browse, clone, download)
   • write (push)
   • ticket tracker
   • exec (???)
   • read (browse)
   • write (create, comment, close, edit)
6. A team SHALL have an options that it has access to ALL repositories of the organisation. If this option is not used then the team MUST be added manually to any repository that it is supposed to have access to.