Aggregate: Host isolation based on image properties

The implementation of the blueprint “Host isolation based on image properties by the way of aggregate metadata” defines that:

- if a host belongs to an aggregate and if this aggregate defines one or several metadata that match with the image properties then the host is a candidate to boot the instance.

- If a host doesn't belong to any aggregate it can create instances from all images.

The goal for this blueprint is to implement a new scheduler filter "AggegateImagePropertiesIsolate" that isolates an image from his properties to a host by the way of an aggregate.

Example:
ubuntu@sf-devel:~$ nova aggregate-details windows
+----+---------+-------------------+------------+--------------+
| Id | Name | Availability Zone | Hosts | Metadata |
+----+---------+-------------------+------------+--------------+
| 1 | windows | None | 'sf-devel' | 'os=windows' |
+----+---------+-------------------+------------+--------------+

ubuntu@sf-devel:~$ glance image-show cirros-0.3.1-x86_64-uec
+------------------+--------------------------------------+
| Property | Value |
+------------------+--------------------------------------+
| Property 'os' | windows |
| checksum | f8a2eeee2dc65b3d9b6e63678955bd83 |
| container_format | ami |
| created_at | 2013-11-14T13:24:25 |
...

The image above will boot on sf-devel.