Added write support for binary files!

Holy cow, this took a lot of work. I think I may need to do a few more
things before I consider this a 1.0 release, but I'm glad to have
finally overcome this hurdle!

Interfaces/IBinaryFileChunk.cs

@@ -0,0 +1,8 @@
+namespace RobloxFiles.BinaryFormat
+{
+    public interface IBinaryFileChunk
+    {
+        void LoadFromReader(BinaryRobloxFileReader reader);
+        BinaryRobloxFileChunk SaveAsChunk(BinaryRobloxFileWriter writer);
+    }
+}

Interfaces/IXmlPropertyToken.cs

@@ -0,0 +1,12 @@
+using System.Xml;
+
+namespace RobloxFiles.XmlFormat
+{
+    public interface IXmlPropertyToken
+    {
+        string Token { get; }
+
+        bool ReadProperty(Property prop, XmlNode token);
+        void WriteProperty(Property prop, XmlDocument doc, XmlNode node);
+    }
+}