Sometimes we wanted to be able to allow some users to add other users, but not change any user's password.
- Adds a new permission 'change other users password'.
- When the user_profile_form is loaded it checks to see if the current user has the proper permission or if they are editing their own account, otherwise it removes the password change option.
- There would be no point restricting the ability to change a user's password if they can still change the user's e-mail address, this option is removed as well.
- This also removes the option to delete a user.