model: Add preliminary support for gen6/gen7

eth: Tweak Ethernet calculation

Move to python3

eth: Add more ethernet rates

pcie: Add support for gen4/gen5 and x32

Adjust Copyright

model: Update __init__.py to export packages

model: Add a model for Intel Niantic style NIC

model: Add a model for a super simple NIC

model: Add utility functions

model: Add models for memory read/write transactions

model: Add Ethernet model

model: Add PCIe model