Scarab LDAP configuration

I was able to integrate the LDAP feature (with Andrey's patch) to Scarab
0.21 and the feature works fine with Active Directory server.  However,
there are other enhancements I wish to have with this LDAP feature.

(1) Provide a way to identify LDAP users vs. non-LDAP users. Perhaps set
TURBINE_USER table CONFIRM_VALUE=COMFORMED-LDAP for LDAP users and
CONFIRM_VALUE=COMFORMED for non-LDAP users. Or add a new column to
identify LDAP users.  The value is set when user is logged in and
synchronized with LDAP server.

(2) Enhance "Reset Password" and "Change Password" functions to generate
a cannot-change-password-locally warning for LDAP users if they attempt
to change password.  For non-LDAP users changing password will proceed
as usual.

(3) When Scarab Administrator adds a new LDAP user, only the "User name"
field is needed and a check box to indicate "Sync with LDAP".  This is
particularly useful when re-register a deleted user, since the deleted
user can't log in to get account generated automatically (maybe should
be configurable if you don't want users to create account
automatically).

Thanks,
JC