Clean up project structure

The number package is moved into its own package henceforth referred
to as "organelle". Hyphae and Mycelium are updated accordingly. In
addition, Hyphae gets a copy of the sexpr module of Mycelium. This
will not remain a copy, rather it will be the basis of a heap manager
module within Mycelium to be worked on in the future.

Fixes #32

Signed-off-by: Ava Affine <ava@sunnypup.io>

mycelium/src/parser.rs

@@ -26,7 +26,7 @@ use crate::lexer::{
     E_CHAR_TOO_LONG,
     E_END_OF_DOCUMENT
 };
-use crate::number::{Number, Numeric};
+use organelle::{Number, Numeric};
 use crate::sexpr::{Datum, Ast};
 
 use alloc::vec::Vec;