snekde: Start creating host-side curses-based helper application

This is a python app designed to edit programs stored on snek devices
and interact with the REPL. It offers to panes in a terminal window,
one for editing code and the other for interacting with the device,
and it can read and write the contents of the eeprom on the target.

Signed-off-by: Keith Packard <keithp@keithp.com>