[network] Define virtual port/device API

[sandersms]

Identify the virtual port/device API to include:
CRUD support for: Create, Update, List, Get, Delete
State: up/down
Statistics: rx, tx
Configuration: MTU, queue, HW Address (MAC)
SR-IOV/SIOV Config:

[sandersms]

Is is possible to combine this with Issue#441 with the Create and Delete only applying to a Virtual port/device? Can the SR-IOV/SIOV Config be applicable only to a virtual device?