Migrate recent HLLib work to BOS

It's better suited for the model of BOS and not an update to HLLibSharp

BurnOutSharp.Models/GCF/Header.cs

@@ -0,0 +1,61 @@
+namespace BurnOutSharp.Models.GCF
+{
+    /// <see href="https://github.com/RavuAlHemio/hllib/blob/master/HLLib/GCFFile.h"/>
+    public sealed class Header
+    {
+        /// <summary>
+        /// Always 0x00000001
+        /// </summary>
+        public uint Dummy0;
+
+        /// <summary>
+        /// Always 0x00000001
+        /// </summary>
+        public uint MajorVersion;
+
+        /// <summary>
+        /// GCF version number.
+        /// </summary>
+        public uint MinorVersion;
+
+        /// <summary>
+        /// Cache ID
+        /// </summary>
+        public uint CacheID;
+
+        /// <summary>
+        /// Last version played
+        /// </summary>
+        public uint LastVersionPlayed;
+
+        /// <summary>
+        /// Reserved
+        /// </summary>
+        public uint Dummy1;
+
+        /// <summary>
+        /// Reserved
+        /// </summary>
+        public uint Dummy2;
+
+        /// <summary>
+        /// Total size of GCF file in bytes.
+        /// </summary>
+        public uint FileSize;
+
+        /// <summary>
+        /// Size of each data block in bytes.
+        /// </summary>
+        public uint BlockSize;
+
+        /// <summary>
+        /// Number of data blocks.
+        /// </summary>
+        public uint BlockCount;
+
+        /// <summary>
+        /// Reserved
+        /// </summary>
+        public uint Dummy3;
+    }
+}