Port some extensions from BOS

This omits anything that relies on caching, at the moment. There is no easy way of creating a cache for the required pieces in the static context of the extensions.

Extensions.CFB.cs

@@ -0,0 +1,36 @@
+using System;
+using SabreTools.Models.CFB;
+
+namespace SabreTools.Serialization
+{
+    public static partial class Extensions
+    {
+        /// <summary>
+        /// Sector size in bytes
+        /// </summary>
+        /// <param name="binary">Binary model to derive from</param>
+        /// <returns>Sector size on success, -1 on error</returns>
+        public static long SectorSize(this Binary binary)
+        {
+            // If we have an invalid header
+            if (binary.Header?.SectorShift == null)
+                return -1;
+
+            return (long)Math.Pow(2, binary.Header.SectorShift);
+        }
+
+        /// <summary>
+        /// Mini sector size in bytes
+        /// </summary>
+        /// <param name="binary">Binary model to derive from</param>
+        /// <returns>Sector size on success, -1 on error</returns>
+        public static long MiniSectorSize(this Binary binary)
+        {
+            // If we have an invalid header
+            if (binary.Header?.SectorShift == null)
+                return -1;
+
+            return (long)Math.Pow(2, binary.Header.MiniSectorShift);
+        }
+    }
+}

Extensions.InstallShieldCabinet.cs

@@ -0,0 +1,33 @@
+using SabreTools.Models.InstallShieldCabinet;
+
+namespace SabreTools.Serialization
+{
+    public static partial class Extensions
+    {
+        /// <summary>
+        /// The major version of the cabinet
+        /// </summary>
+        /// <param name="cabinet">Cabinet model to derive from</param>
+        /// <returns>Major version on success, -1 on error</returns>
+        public static int MajorVersion(this Cabinet cabinet)
+        {
+            // If we have an invalid header
+            if (cabinet.CommonHeader?.Version == null)
+                return -1;
+
+            uint majorVersion = cabinet.CommonHeader.Version;
+            if (majorVersion >> 24 == 1)
+            {
+                majorVersion = (majorVersion >> 12) & 0x0F;
+            }
+            else if (majorVersion >> 24 == 2 || majorVersion >> 24 == 4)
+            {
+                majorVersion = majorVersion & 0xFFFF;
+                if (majorVersion != 0)
+                    majorVersion /= 100;
+            }
+
+            return (int)majorVersion;
+        }
+    }
+}