Draw the tyre gauge as the kart from behind #352

Builds the tyre gauge icon in ADR 0104, chosen in #303. Blocked by #349.

Change

• The tyre gauge draws the own kart from behind in its livery: rear wing across the top, the two big rear tyres either side, the driver's head above the tub.
• The two rears keep data-tyre-corner and the wear band styles. Tyre life is one number, so hiding the fronts loses nothing.
• Retire kartFromAbove. The tyre block drawing stays, under a name that no longer says "above".
• The percentage and data-tyre-wear stay as they are.
• Update the gauge's entry and the from-above rule in docs/style-guide.html, and "drawn from above" under tyre life in docs/GLOSSARY.md.

Done when

A smoke test shows the gauge in the good, warn and bad bands, with the tyres toned by the band and the driver's hair in the kart's own colour.

Spec

docs/mockups/coin-and-tyre-gauge-variations.html, tyre gauge take 3.