Separate the Shell instance and the proper binary module

Cargo.lock

manual/src/builtins.md

src/lib/builtins/command_info.rs

src/lib/builtins/mod.rs

src/lib/builtins/set.rs

src/lib/builtins/status.rs

src/lib/lib.rs

src/lib/shell/assignments.rs

src/lib/shell/binary/designators.rs

src/lib/shell/binary/history.rs

src/lib/shell/binary/mod.rs

src/lib/shell/binary/prompt.rs

src/lib/shell/binary/readln.rs

src/lib/shell/flow_control.rs

src/lib/shell/fork.rs

src/lib/shell/mod.rs

src/main.rs