Besides minor stylistic updates, 3 things changed: 1) switch to compu…

…ting "minimal diffs" when updating sensors, and "only" (mostly) update the ones that have changed in the last sampling interval, rather than redrawing all of them, 2) change RXM into a class rather than a struct (although most access is still left as public, rather than engender more massive code churn), and 3) back off a bit from going "rvalue-reference wild" in the previous commits.