- improve IPv6 RA handling

- support ethtool/sysctl knobs (TSO, LRO, txqueuelen)

- inspecting current network config via "netplan show $interface" for a
  collated view of each interface's yaml.

- debugging config generation via "netplan diff [backend|system]":
  - netplan diff system: compare generated config with current ip addr output
  - netplan diff backend: compare generated config with current config for backend

- better handle VLAN Q-in-Q (mostly generation tweaks + patching backends)

- support device aliases (eth0 + eth0.1; add eth0 to multiple bridges)
  - workaround for two bridges is to use eth0 and vlan1

- make errors translatable

- "netplan save" to capture kernel state into netplan YAML.

- better parsing/validation for time-based values (ie. bond, bridge params)

- better parsing/validation for all schema

- integrate 'netplan try' in tmux/screen

- add automated integration tests for WPA Enterprise / 802.1x that can run self-contained

# After soname bump (ABI break)

- change route->scope to ENUM

- move tunnel_ttl into tunnel struct

- store match.driver as a list rather than a string
