This change introduces the new heat::trustee class to manage
the parameters in the [trustee] options. These options have been set
according to authtoken parameters but it makes maintenance complicated
and the logic doesn't work properly when noauth is used.
This change also removes the [trustee] project_domain_name parameter
because the parameter has never been used actually.
Change-Id: I694a8ea771cc4d4dcfbf8384ece2be10d83ab3f0
