peterwolf's Splinecart

## 0.4.9+26.2

- Steel is the default support mode for new tracks (`/splinecart supports steel`,
  also `stal` / `slup` / `pillar`), including command-built and manually linked tracks.
- Steel construction uses a third rail under the sleepers and thin dark-gray
  pillars every 10-15 blocks, narrowed and pulled into the third rail at the top.
- Pillar spacing is measured along the whole spline so chain-drive segments no
  longer place a support at every tie.
- Track Ties can be placed in mid-air one block from the player: under the feet
  when looking down, directly in front when looking ahead, above the head when
  looking up.
- Placement orientation follows look direction: down is floor/horizontal, ahead
  is wall/sideways, up is ceiling/upside down.