Secure Transacted File System (STFS) Support (#78)

* Initial STFS support

* Fix build errors

* Fix more build errors

* Final fix

* Cleanup printer

* Fix indent

SabreTools.Data.Models/STFS/HashTableEntry.cs

@@ -0,0 +1,33 @@
+using System.Collections.Generic;
+using SabreTools.Numerics;
+
+namespace SabreTools.Data.Models.STFS
+{
+    /// <summary>
+    /// STFS Hash Table Entry in a Hash Block's Hash Table
+    /// </summary>
+    /// <see href="https://free60.org/System-Software/Formats/STFS/"/>
+    public class HashTableEntry
+    {
+        /// <summary>
+        /// SHA-1 hash of the block
+        /// </summary>
+        public byte[] Hash { get; set; } = new byte[20];
+
+        /// <summary>
+        /// Status of the block
+        /// 0x00 = Unused block
+        /// 0x40 = Free block (previously used, now freed)
+        /// 0x80 = Used block
+        /// 0xC0 = Newly allocated block
+        /// </summary>
+        public byte Status { get; set; }
+
+        /// <summary>
+        /// Block number corresponding to the hash
+        /// FFFFFF = Block 1 (starting 0xB000)
+        /// </summary>
+        /// <remarks>Big-endian, 3-byte uint24</remarks>
+        public UInt24 BlockNumber { get; set; } = new();
+    }
+}