core: Foreman discovery host integration to ovirt

Enhance foreman integration for retrieving discovery hosts information
and provide "provision action" which installs bare metal host by using
foreman API. During installation Host life cycle will hold new status
called "Installing OS".

Wiki: http://www.ovirt.org/Features/AdvancedForemanIntegration

Change-Id: I0c25a544373d8ab4a7123137c8a4697205a8efa8
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1083993
Signed-off-by: Yaniv Bronhaim <ybronhei@redhat.com>