Add and use SpamSum for Media and Rom types

SpamSum implementation courtesy of https://github.com/aaru-dps/Aaru

SabreTools.Library/External/Aaru/IChecksum.cs

@@ -0,0 +1,58 @@
+// /***************************************************************************
+// Aaru Data Preservation Suite
+// ----------------------------------------------------------------------------
+//
+// Filename       : IChecksum.cs
+// Author(s)      : Natalia Portillo <claunia@claunia.com>
+//
+// Component      : Checksums.
+//
+// --[ Description ] ----------------------------------------------------------
+//
+//     Provides an interface for implementing checksums and hashes.
+//
+// --[ License ] --------------------------------------------------------------
+//
+//     Permission is hereby granted, free of charge, to any person obtaining a
+//     copy of this software and associated documentation files (the
+//     "Software"), to deal in the Software without restriction, including
+//     without limitation the rights to use, copy, modify, merge, publish,
+//     distribute, sublicense, and/or sell copies of the Software, and to
+//     permit persons to whom the Software is furnished to do so, subject to
+//     the following conditions:
+//
+//     The above copyright notice and this permission notice shall be included
+//     in all copies or substantial portions of the Software.
+//
+//     THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+//     OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+//     MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+//     IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+//     CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+//     TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+//     SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//
+// ----------------------------------------------------------------------------
+// Copyright © 2011-2020 Natalia Portillo
+// ****************************************************************************/
+
+namespace Aaru.CommonTypes.Interfaces
+{
+    public interface IChecksum
+    {
+        /// <summary>Updates the hash with data.</summary>
+        /// <param name="data">Data buffer.</param>
+        /// <param name="len">Length of buffer to hash.</param>
+        void Update(byte[] data, uint len);
+
+        /// <summary>Updates the hash with data.</summary>
+        /// <param name="data">Data buffer.</param>
+        void Update(byte[] data);
+
+        /// <summary>Returns a byte array of the hash value.</summary>
+        byte[] Final();
+
+        /// <summary>Returns a hexadecimal representation of the hash value.</summary>
+        string End();
+    }
+}