Include domain name in name of hosts
Pass plugins into reassigning
Add the plugin to controll assignment of nodes

The patch adds the `assignment` plugin to provide the control how new
nodes will be configured in the destination cloud. The configuration
contains disks, interfaces and roles. The plugin works in two modes such
as `fixed` and `discover`. The `fixed` means that configuration
specified in PLUGINS section like this:

    PLUGINS:
        assignment: fixed # fixed/discovery
        assignment_parameters: # in case of assignment_config=fixed
            roles:
                - compute
                - cinder
            disks:
                - name: sda
                  size: 11427148
                  volumes:
                  - name: os
                    size: 0
                  - name: cinder
                    size: 5713574
                  - name: vm
                    size: 5713574
                - name: sdb
                  size: 190090
                  volumes:
                  - name: os
                    size: 190090
                  - name: cinder
                    size: 0
                  - name: vm
                    size: 0
                - name: sdc
                  size: 190090
                  volumes:
                  - name: os
                    size: 0
                  - name: cinder
                    size: 0
                  - name: vm
                    size: 190090
            ifaces:
                - name: eth0
                  assigned_networks:
                  - fuelweb_admin
                - name: eth1
                  assigned_networks: []
                - name: eth2
                  assigned_networks:
                  - public
                - name: eth3
                  assigned_networks:
                  - management
                  - storage
                  - fixed

The `discovery` means that the configuration will be got from the first
random compute node.
merge reassignment with fixed configuration option