add a separate bus mode cache for each interface.
add property objects to config frame for setting/getting from bus mode cache.
update function update_bus_modes to fit changes to bus mode cache
only create a banner frame for potato version (since it hold info about submixes).
stick nav_frame eastwards.
change columnspan for bus config frame to 4 to match strip config frames.
strip/bus levels compared by index iteratively.
strip/bus level array size added to _base_vals dataclass. Helps to keep track of level array size when switching between kinds.
level_offset class attributes added to strip/bus/gainlayer labelframe classes.
watch_levels adjusted to only updated frames when a level has changed.
ldirty added, true iff level value has changed.
fetching level arrays moved to highest level of the app.
pdelay and ldelay added to _base_vals dataclass.
