rename "microbit" package to "core" #414 (#270)

* rename "microbit" package to "core" #414

* shouldn't edit the package id.

* updating package.json

* updated the wrong version

* missed updating pxt.json of tests

libs/core/messages.ts

@@ -0,0 +1,51 @@
+namespace messages {
+    var streamid: string;
+        
+    export function setStreamId(id: string) {
+        streamid = id;
+    }
+    
+    /**
+     * Creates a new message that includes the board serial number and the stream id if any
+     */
+    export function createMessage() : Message {
+        let m = new Message();
+        m.addNumber('board', control.deviceSerialNumber());
+        if (streamid != null && streamid.length > 0)
+            m.addString('stream', streamid);
+        return m;
+    }
+    
+    /**
+     * A message containig custom data
+     */
+    export class Message {
+        private buffer:string = '';
+        
+        /**
+         * Adds a string field to the message
+         */
+        //%
+        public addString(name:string, value:string) {
+            if (this.buffer.length > 0) this.buffer += ',';
+            this.buffer += name + ':"' + value + '"';
+        }
+        
+        /**
+         * Adds a number field to the message
+         */
+        //%
+        public addNumber(name:string, value: number) {
+            if (this.buffer.length > 0) this.buffer += ',';
+            this.buffer += name + ':' + value;            
+        }
+        
+        /**
+         * Converts the message to a JSON payload
+         */
+        //%
+        public toJSON() : string {
+            return '{' + this.buffer + '}';
+        }        
+    }
+}