Add support for retrieving the current system date/time

#56

messages/SLGetSystemTime.js

@@ -0,0 +1,37 @@
+'use strict';
+
+const SLMessage = require('./SLMessage.js').SLMessage;
+
+const MSG_ID = 8110;
+
+exports.SLGetSystemTime = class SLGetSystemTime extends SLMessage {
+  constructor(buf, senderId) {
+    if (buf) {
+      var size = buf.readInt32LE(4) + 8;
+      super(buf, MSG_ID, size);
+    } else {
+      super(senderId, MSG_ID);
+    }
+  }
+
+  decode() {
+    super.decode();
+
+    this.year = this.readUInt16LE();
+    this.month = this.readUInt16LE();
+    this.dayOfWeek = this.readUInt16LE();
+    this.day = this.readUInt16LE();
+    this.hour = this.readUInt16LE();
+    this.minute = this.readUInt16LE();
+    this.second = this.readUInt16LE();
+    this.millisecond = this.readUInt16LE();
+    var adjustForDST = this.readInt32LE();
+    this.adjustForDST = adjustForDST === 1;
+
+    this.date = new Date(this.year, this.month - 1, this.day, this.hour, this.minute, this.second);
+  }
+
+  static getResponseId() {
+    return MSG_ID + 1;
+  }
+};