AuthCrypt allows for StatusNet and GNU social to use crypt() hashing to store password credentials.

Requirements
============
Nothing out of the ordinary (SHA512 is supported natively since PHP 5.3.2)

Installation
============
Add either of the following configurations to your config.php (see Example below for more options):

The recommended use is to overwrite old hash values when logging in (statusnet + overwrite modes) and be the authority on password checks when logging in. If you only wish to update entries on password change the default values are enough. 'statusnet' and 'overwrite' are true by default. 'authoritative' is only necessary if we want to exclude other plugins from verifying the password.

    addPlugin('AuthCrypt');

To disable updating to crypt() on password change (and login with the 'statusnet' compatibility mode), simply set the 'overwrite' setting to false:

    addPlugin('AuthCrypt', array(
        'overwrite'=>false,
    ));

Settings
========
Default values in parenthesis. Many settings are inherited from the AuthenticationPlugin class.

authoritative (false): Set this to true when _all_ passwords are hashed with crypt()
    (warning: this may disable all other password verification, also when changing passwords!)
hash ('$6$'): Hash signature to use, defaults to SHA512. See all supported strings at http://php.net/crypt
    (warning: set this to something crypt() understands, or you will default to the very weak 2-char DES scheme)
statusnet (true): Do we check the password against legacy StatusNet md5 hash?
    (notice: will check password login against old-style hash and if 'overwrite' is enabled update using crypt())
overwrite (true): Do we overwrite old style password hashes with crypt() hashes on password change?
    (notice: to make use of stronger security or migrate to crypt() hashes, this must be true)
password_changeable (true): Enables or disables password changing.
    (notice: if combined with authoritative, it disables changing passwords and removes option from menu.)
autoregistration: This setting is ignored. Password can never be valid without existing User.
provider_name: This setting defaults to 'crypt' but is never stored anywhere.
