Cloudstack Driver - Create/Delete Network functionality + tests

Functions added on the cloudstack driver:
 
ex_list_network_offering
ex_create_network
ex_delete_network

New Object:
CloudStackNetworkOffering

And some additions to the CloudStackNetwork dictionary
netmask
gatway
vpcid
You still need to fix the kwargs issue. We prefer to explicitly list the arguments that you need: gateway, net mask, vpc_id