Rename Stack object to Overcloud
Rename Stack object to Overcloud

Tuskar will have to store additional information
about each stack to deal with the overcloud
configuration.  That means Overcloud is a more
precise name.

Change-Id: Icda83a26ada1f57203d64627c270c35b9bbf2b58

rdo-management/tuskar-ui,rdo-management/tuskar-ui,rdo-management/tuskar-ui,rdo-management/tuskar-ui