Common usage is REST, and most in project are written as REST.
Change ReST to REST to comply with it.
Change-Id: I2c87f4c811f7dd64a3f5807a45eba2a82373da36
Uses openstackdocstheme to match other content
Has a dependent change in project-config also so that
file will build to developer.openstack.org/compute
at https://review.openstack.org/#/c/231000/
Change-Id: Ic060a1e79e4b2f8695cb788ff4df018e0cfd3286