BLE UART Buffer methods (#1353)

* adding simulator

* attempt at handling size

* correct ref counting

* defense is on

* handle read < 0

libs/bluetooth/shims.d.ts

@@ -63,6 +63,18 @@ declare namespace bluetooth {
     //% parts="bluetooth" advanced=true shim=bluetooth::startUartService
     function startUartService(): void;
 
+    /**
+     * Sends a buffer of data via Bluetooth UART
+     */
+    //% shim=bluetooth::uartWriteBuffer
+    function uartWriteBuffer(buffer: Buffer): void;
+
+    /**
+     * Reads buffered UART data into a buffer
+     */
+    //% shim=bluetooth::uartReadBuffer
+    function uartReadBuffer(): Buffer;
+
     /**
      * Registers an event to be fired when one of the delimiter is matched.
      * @param delimiters the characters to match received characters against.