Add basic support for Public.lua lib

[trentgill]

Based off pydfu branch.

Enables 1 key new functionality public.view which is used to keep the host (druid) informed of the CV states of the physical crow.

public.view.all() enables tracking of all inputs & outputs. the top-bar status indicator is now somewhat more cramped and won't work well on very narrow screen widths.

NB: the values only update if they have changed by 0.1V and are throttled to ~15fps to avoid too much strain on the usb pipe.

Other changes just filter out public specific ^^ commands so they don't flood the terminal (they are not intended to be user-facing).

Final change is a newline is added after a ^^ command that is printed to the console. Previously there would be no line separation and multiple sequential messages were far harder to observe the changes. Now things are aligned vertically so it's easier to see how a stream of values is changing over time.

Fixes #13