Add proper handling of passwords

- Encryption using Crypt::SaltedHash
- Repeated password field, including checks for matching passwords
- Passwords are entered as part of registering a new user, but
  editing is done in a separate screen
- Passwords are checked for length
- Forms "enforce" minimum password length from config (min_pass)
- Sample data is updated with hashed passwords
Add a comment to db/schema.sql with sample passwords in plain text
Move setting for minimum password length to environment files