core: add GetImageByIdQuery

Change-Id: I53f05023301df81fc66d4ff36bc98369ae15a3f7
Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>
restapi: add ReadOnlyResource

Change-Id: Ic77b92b0e696e8ad0a0095006772320ac2f0600a
Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>
restapi: image entity and import from glance

This patch adds an initial implementation for the REST API commands to
import and export images from and to image storage domains (as OpenStack
Glance).

The API at the moment has to be intended as Technology Preview and it
might be subject to changes in the future.

Glance integration feature page:

 http://www.ovirt.org/Features/Glance_Integration

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=990962
Change-Id: Ief9104ff0eba175c90b42bc5651ada0f688eeb00
Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>