Allow for selection of floating IP pool in OpenStack

[bhagemeier]

The script currently selects floating IP pool 'public_ips', which is usually very site specific. We need to define a means to retrieve the correct floating IP pool to use. This could be done in the MarketPlace (is it possible to add arbitrary information?), the Information System (which information item?), or possibly with a specific flag on the pool's description, as it can be retrieved via the OCCI API.