Fixups from code review

- Remove WeDo 2 extension from the runtime's default block packages list
- The WeDo 2.0 extension now calls its own `connect` method on startup

I also renamed `EXTENSION_NAME` to `EXTENSION_ID` for consistency with
the rest of the extension system.

src/blocks/scratch3_wedo2.js

@@ -373,9 +373,9 @@ const TiltDirection = {
 class Scratch3WeDo2Blocks {
 
     /**
-     * @return {string} - the name of this extension.
+     * @return {string} - the ID of this extension.
      */
-    static get EXTENSION_NAME () {
+    static get EXTENSION_ID () {
         return 'wedo2';
     }
 
@@ -397,7 +397,7 @@ class Scratch3WeDo2Blocks {
          */
         this.runtime = runtime;
 
-        this.runtime.HACK_WeDo2Blocks = this;
+        this.connect();
     }
 
     /**
@@ -405,7 +405,7 @@ class Scratch3WeDo2Blocks {
      */
     getInfo () {
         return {
-            id: 'wedo2',
+            id: Scratch3WeDo2Blocks.EXTENSION_ID,
             name: 'WeDo 2.0',
             blocks: [
                 {
@@ -586,7 +586,7 @@ class Scratch3WeDo2Blocks {
         }
         const deviceManager = this.runtime.ioDevices.deviceManager;
         const finder = this._finder =
-            deviceManager.searchAndConnect(Scratch3WeDo2Blocks.EXTENSION_NAME, WeDo2.DEVICE_TYPE);
+            deviceManager.searchAndConnect(Scratch3WeDo2Blocks.EXTENSION_ID, WeDo2.DEVICE_TYPE);
         this._finder.promise.then(
             socket => {
                 if (this._finder === finder) {

src/engine/runtime.js

@@ -23,8 +23,7 @@ const defaultBlockPackages = {
     scratch3_sound: require('../blocks/scratch3_sound'),
     scratch3_sensing: require('../blocks/scratch3_sensing'),
     scratch3_data: require('../blocks/scratch3_data'),
-    scratch3_procedures: require('../blocks/scratch3_procedures'),
-    scratch3_wedo2: require('../blocks/scratch3_wedo2')
+    scratch3_procedures: require('../blocks/scratch3_procedures')
 };
 
 /**