[REF] qweb: split code into 3 files

closes #84

src/index.ts

@@ -1,8 +1,13 @@
 export { Component } from "./component";
 export { EventBus } from "./event_bus";
 export { Observer } from "./observer";
-export { QWeb } from "./qweb";
+
+import "./qweb_directives";
+import "./qweb_extensions";
+export { QWeb } from "./qweb_core";
+
 export { connect, Store } from "./store";
 import * as _utils from "./utils";
 
+
 export const utils = _utils;