Update/add instructions in parser

* StoreImm just uses a u64 instead of u32 - we'll figure out the layout
  later
* Jmp implementation added (can't believe I forgot this)
* Add Inst AST item, whose immediates don't have to be a u64 right away

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/main.rs

@@ -25,6 +25,6 @@ fn main() -> Result<()> {
             process::exit(1);
         },
     };
-    println!("{:?}", ast);
+    println!("{:#?}", ast);
     Ok(())
 }