Migrate recent HLLib work to BOS

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

BurnOutSharp.Models/GCF/BlockEntry.cs

@@ -0,0 +1,41 @@
+namespace BurnOutSharp.Models.GCF
+{
+    /// <see href="https://github.com/RavuAlHemio/hllib/blob/master/HLLib/GCFFile.h"/>
+    public sealed class BlockEntry
+    {
+        /// <summary>
+        /// Flags for the block entry.  0x200F0000 == Not used.
+        /// </summary>
+        public uint EntryFlags;
+
+        /// <summary>
+        /// The offset for the data contained in this block entry in the file.
+        /// </summary>
+        public uint FileDataOffset;
+
+        /// <summary>
+        /// The length of the data in this block entry.
+        /// </summary>
+        public uint FileDataSize;
+
+        /// <summary>
+        /// The offset to the first data block of this block entry's data.
+        /// </summary>
+        public uint FirstDataBlockIndex;
+
+        /// <summary>
+        /// The next block entry in the series.  (N/A if == BlockCount.)
+        /// </summary>
+        public uint NextBlockEntryIndex;
+
+        /// <summary>
+        /// The previous block entry in the series.  (N/A if == BlockCount.)
+        /// </summary>
+        public uint PreviousBlockEntryIndex;
+
+        /// <summary>
+        /// The offset of the block entry in the directory.
+        /// </summary>
+        public uint DirectoryIndex;
+    }
+}