Add live visualization TUI

[jdhoffa]

This should probably be a whole Milestone...

Some type of terminal TUI or user interface showing live feeder load vs. schedule and watch curve updates.
Maybe allow some minor scenario configuration from the UI.

https://github.com/aksakalli/gtop for style and design inspiration

[jdhoffa]

$Proposed decomposition:\n- [ ] https://github.com/jdhoffa/vpp-sim/issues/50\n- [ ] https://github.com/jdhoffa/vpp-sim/issues/51\n- [ ] https://github.com/jdhoffa/vpp-sim/issues/52\n- [ ] https://github.com/jdhoffa/vpp-sim/issues/53\n- [ ] https://github.com/jdhoffa/vpp-sim/issues/54\n\nParent #28 is done when all child issues are closed and README includes usage/keybindings.