system users should not have email address

[brianmay]

Carrying discussion from #286, is no longer related to this pull request.

@bjmoran Just trying to understand use case requirements for new design for Karaage. So I can come up with the best design that doesn't accidentally break existing use cases.

Currently the rule is that system users (including training accounts) can have a shared email address.

If we were to - hypothetically speaking - implement a rule that system users cannot have any email address. Would this break anything? Would be be better or worse?

Would it also be reasonable to say that system user's should not be able to make changes to their Karaage account details - this should always be done by a system administrator?