Fixing issue #167 along with problem reported on the list by Pat Alle…

Created by: dverdin

Fixing issue #167 (closed) along with problem reported on the list by Pat Allen: password was reset when subscribing to a list. When updating a user, password was systematically rehashed even if it was not a new password. Consequently, anytime a user was updated, the password replaced y its own hash. Fixed by checking the database for a pre-existing password before computing the hash.