Implemented AdvNetworking scenarios via Neutron

Added a new package ( io.murano.lib.networks.Neutron) to handle networking via Neutron
The package introduces a class 'NewNetwork' (io.murano.lib.networks.neutron.NewNetwork)
This class is capable of the following:
 - Create a new Network (L2 segment)
 - Use NetworkExplorer class to allocate an available CIDR
 - Create a new Subnet (L3 segment) in the created Network with the allocated CIDR
 - Use NetworkExplorer class to locate an available router
 - Use NetworkExplorer class to detect the default DNS nameserver
 - Uplink the created subnet to the located router

Also, as this class extends io.murano.resources.Network, it implements the addHostToNetwork method
The implementation creates a Neutron Port and connects that port to a created network and intance

 This commit also modifies the environment-creation logic of the API, allowing to add default networks
 to the Environment object.
 This is a temporary solution: in future the instantiation of this object(s) should be done in MuranoPL

 This commit concludes the minimum set of functionality needed to implement AdvancedNetworking
 in 0.4.x feature set.

 Closes-bug: #1308921

Change-Id: I885620099995b0d402a23def3ff428fb902973d2
Merge "Implemented AdvNetworking scenarios via Neutron"