implement thread shared systems

src/circuit.rs

src/cli.rs

src/main.rs

src/prog.rs

src/projective.rs

src/traits/mod.rs

src/traits/system.rs

src/traits/track.rs

src/traits/track/distort.rs

src/traits/track/extend.rs

src/traits/track/find_moore_box.rs

src/traits/track/one_step.rs

src/traits/track/refine.rs

src/traits/track/to_chart.rs

tests/arb_reckless_track.rs

tests/flint_track.rs

tests/parser.rs

tests/projective.rs

tests/track.rs