re #21 add the update_seller_user service method
re #21 unit test the update_seller_user method
re #21 add error/success messages in the template of the password
edition
re #21 add the message attribute in the parent view to be able to manage
the error and success messages in all views
re #21 integrate the update password featurein the settings user view
re #21 use globale variables for the max and min sizes of password
Merge pull request #42 from jean553/fix_21

Fix 21 - Integrate seller user password update feature