v0.2.13 — the signal score becomes Link health

The 0–100 "Signal" score counted ping, so a clean link far from its ground
station read red: 90 ms with no drops scored 39. It also let 5% packet loss read
95 and stay cyan. The score now describes the link rather than the distance, and
it has a name to match.

Expect your number to change. High-ping dishes will read much higher, and
dishes that are dropping packets will read lower.

• Renamed. The score is now Link health: LINK on the panel gauge, link
  in the menu-bar tooltip, and Health in the terminal dashboard. Your readout
  settings carry over.
• Ping no longer counts. It keeps its own readout.
• Drops count six times over. 1% reads 94, 5% reads 70 (amber), 10% reads 40
  (red), and about 17% or more reads 1.
• 0 means no internet. It appears only when the dish is not connected or every
  ping was lost. Any working connection scores at least 1 and lights at least one
  bar. A dish that was not connected could previously score high if its drop rate
  happened to read 0%.
• Terminal fix. The bash sl could show a score one point away from the Go
  build, enough to change its colour.

The score uses the latest drop reading rather than an average, so one bad second
can move it briefly.

The JSON key is still signalScore, and the Signal bars menu-bar glyph keeps
its name.