most python api should be in plural

[Wumpf]

i.e. log_point should go away and be taken over by log_points (still the same api)

[emilk]

log_points should then have the ergonomics of log_point, e.g. not having to wrap in extra array

[emilk]

We've decided never to add log_images or log_tensors, and instead treat each value in a tensor as an instance:

• Treat tensor values as instances #1756

[emilk]

We're rewriting the API now; this will now be handled by archetypes