Feature: Password reset

[tmaex]

Ability to reset my own password by mail.

[fabianlipp]

This would mean a change for the permissions because we would need a system user who can change the other users' passwords. At the moment there are no users with write permission whose passwords are stored on the server, whiche is nice from a security perspective.
Actually this is the reason why I didn't implement this from the beginning.

If we had such a system user, we could also think of changing the registration process in a way that the user doesn't get his password by mail but instead a link to a registration page to choose his own password.