Separate the parser and the expansion into sub-modules

src/binary/completer.rs

src/binary/mod.rs

src/binary/prompt.rs

src/lib/assignments/actions.rs

src/lib/assignments/checker.rs

src/lib/assignments/mod.rs

src/lib/builtins/variables.rs

src/lib/expansion/loops.rs

src/lib/expansion/methods/arrays.rs

src/lib/expansion/methods/mod.rs

src/lib/expansion/methods/strings.rs

src/lib/expansion/mod.rs

src/lib/expansion/pipelines.rs

src/lib/expansion/words/mod.rs

src/lib/expansion/words/tests.rs

src/lib/lib.rs

src/lib/parser/mod.rs

src/lib/parser/pipelines.rs

src/lib/parser/statement/parse.rs

src/lib/shell/assignments.rs