Big Object naming refactor

* trait Obj -> Object
* Remove *Inst suffix from all object types. ObjInst -> Obj, IntInst ->
  Int, etc
* Type -> Ty, type_inst() -> ty(), type_name() -> ty_name()

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

src/obj/macros.rs

@@ -7,7 +7,7 @@ macro_rules! impl_base_obj {
                     .expect(concat!("no ", stringify!($type_name)))
                     .clone()
             });
-            self.set_attr("__type__", ty);
+            self.set_attr("__ty__", ty);
             self.$base_name.instantiate();
         }