Improve SDN Features, Packet Transforms and Scale document

[mmiele]

This issue collects information and related PRs intended to improve the document: SDN Features, Packet Transforms and Scale
Tasks that may produce related documentation:

• Routing guidelines. WIP, see doc-routing-guidelines (draft) #67
• Packet Flow and Transforms. WIP, see move-packet-flow-transforms #114
• VM to VM communication scenario in VNET. Work in draft form not yet available for PR
• Support features such as Telemetry, Metering, Counters, Billing, Watchdogs, BGP?
• Servicing
• Update SDN Features, Packet Transforms and Scale accordingly. WIP.