Add --set-nt-hash option to pdbedit to update user password from nt-hash hexstring.

Useful to take in sync password from other repository.
(Modify MASK_USER_GOOD to include new flag  BIT_PWSETNTHASH)

pdbedit -vw show also  password hashes .

Split pdb_set_plaintext_passwd  in two function:
pdb_set_plaintext_passwd and pdb_update_history.
pdb_update_history update password history and is call from
pdb_set_plaintext_passwd.

Signed-off-by: Alberto Maria Fiaschi <alberto.fiaschi@estar.toscana.it>
Reviewed-by: Garming Sam <garming@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
