Added Function Tables

- Ftable struct
- CallFunction procedure
- Refactors to Cell, Ctr (consequently to lex too)
- More recursive routines in Cell

src/lib.rs

@@ -17,8 +17,12 @@
 
 mod cell;
 mod lex;
+mod func;
+mod eval;
 
 pub mod ast {
     pub use crate::cell::{Cell, Ctr, cons, cell_as_string};
     pub use crate::lex::{lex};
+    pub use crate::func::{Function, Operation, FTable};
+    pub use crate::eval::{eval};
 }