Update automatic code generation tools

[acloudiator]

https://github.com/polycube-network/swagger-codegen/ is behind last changes we did to polycube.

AFAIK this as the missing changes:

• Ports constructor
• Ports::{create, get, getEntry, remove, removeEntry}
• packet_in signature
• remove TYPE_ from TYPE_{TC, XDP_SKB, XDP_DRV}
• egress_code argument always required in Cube constructor
• Cube is templated: cube inherits from Cube
• ports_ is not anymore present on service class (not sure if this is part of the code generator)
• CMakeList.txt on src/
• create service_dp.c instead of service_dp.h
• do not include datamodel in service-lib.cpp

Probably we should adopt a policy that a PR that affects code generation cannot be merged into polycube until the generation tools are updated

• Mauricio

[mauriciovasquezbernal]

solved by:
polycube-network/pyang-swagger#3
polycube-network/swagger-codegen#3