- Drop `use flowscad::*;` from src/bitcube3.rs, src/bitcube4.rs, src/bitperm5.rs.
- Remove `impl From<BitCubeN> for D3` blocks that duplicated impls already
  provided by flowscad 0.2.0's src/scad3d.rs. Downstream users see no API change.
- Move flowscad-using examples (scad_cube, scad_rotate, scad_test_rotate_y) out
  of this crate; they now live in flowscad's gallery/ where they belong.
- Drop `flowscad` from [dependencies]; bitperm no longer depends on flowscad.

This breaks the flowscad <-> bitperm circular dependency and allows flowscad
to depend on bitperm from crates.io by version.

Bump version to 0.2.0.

Co-authored-by: Cursor <cursoragent@cursor.com>