Implement optional type parameters (#360)

* Add a NATIVE<T> macro type to simplify use of a native WebAssembly type
* Add default type parameters for internal helpers for explicit loads and stores
* Unify loadUnsafe/loadUnsafeWithOffset etc. into one
* Renamed loadUnsafe etc. into just LOAD, like a macro
* Implement parsing of index signatures, but ignore them, for properly linting code
* Refactor TypedArray<T> to use macros

std/assembly/string.ts

@@ -11,7 +11,7 @@ import {
 } from "./internal/string";
 
 import {
-  storeUnsafe as storeUnsafeArray
+  STORE
 } from "./internal/arraybuffer";
 
 @sealed
@@ -436,7 +436,7 @@ export class String {
           ),
           HEADER_SIZE
         );
-        storeUnsafeArray<String,String>(buffer, i, char);
+        STORE<String>(buffer, i, char);
       }
       return result;
     } else if (!length) {