Update astakos actions

This patchset makes the following changes in astakos actions:

* `accept`: Accept only unmoderated or rejected users.
* `deactivate`: Deactivate only moderated users. This includes inactive
  users, solely for the purpose of changing their deactivation reason.
* `send_verification_mail`: Renew verification code and send it only to
  users with unverified mail.

Last, it updates the `user_logic.py` tests according to the above changes.

Proposed reviews: @vinilios