Added CLI option to specify channel number, but I'm not sure it's really
working. Refactored AppConfig a little. Added threshold indication on
status bar. References and UI are separate settings and can be toggled
individually. At least 1 sample is always shown when discarding due to
triggering. Range and threshold are configured with arrow keys. Added
more colors to palette. Added ability to toggle braille mode. Fix: fully
write "fps" instead of cutting "s" out.
it's now possible to change most settings while scope-tui. Keybinds are
`v` for vectorscope/oscilloscope, `s` for scatter/line and `+/-` to
manage range.
