[Fix] Remove the support of reduce from rustc, it was not trivially implementable for the general case.
[AST] Add Zero or more operator  to the AST, implementation doing nothing for the moment.
[Refactor] Put the compiler in a struct, useful to keep an environnement (list of top level items, current rule, unique id generator).
[Grammar] Finalize the zero or more operator , generates the code. It closes #5.