Navigator should ensure Pilots are up to date

[munnerz]

It's important that pilots are kept reasonably up to date with the navigator controller, in-line with our (TBD) backwards compatibility/versioning policy.

This will otherwise become a regular maintenance burden of consumers of the navigator api (e.g. developers), who will require a knowledge of the versions that navigator itself supports.

Ideally, navigator itself would take care of selecting a pilot image to use (potentially retaining the ability to manually specify an image). This would happen through the usual upgrade process for that particular resource.

/kind feature