[tryton-dev] create basic password field

[Demoy Blake]

I want create a password field (a field that does not echo user input)
 to accept password from the client when needed.
 the input of this password field should not encrypted . 

I tried to use a sha field for this, but I must have missunderstood the 
documentation because the field won't appear in my views.

                      MPass=fields.Sha('MITS 
password',required=True,help='')