Keyline Icons v0.4.0: Every sharp end cut back

Every sharp diagonal end is cut back to its round cap's box, on 329 icons: the chevrons, arrowheads, signs and slashes that painted 0.414 outside their rounded siblings sit on the same box now, and every arc the converter had bent by moving its endpoint is a true arc again. settings-dot's sharp gear is cut on its cap's own line, so its grey plate ends flush with the black instead of escaping past it, and circle-navigation sits centred in its box.

43 drawings added since 0.3.0, bringing the set to 629, and 315 redrawn.