Removed NioTSO client and server

- NioTSO client isn't needed because we're using RayLib
- Added FreeSO's API server to handle most backend operations

server/FSO.Server.Protocol/Utils/ChallengeResponse.cs

@@ -0,0 +1,77 @@
+using System;
+using System.Collections.Generic;
+using System.Security.Cryptography;
+using System.Text;
+
+namespace FSO.Server.Protocol.Utils
+{
+    public class ChallengeResponse
+    {
+        private static int _salt_byte_length = 320;
+        private static int _nonce_byte_length = 32;
+        private static RNGCryptoServiceProvider _random_crypt_prov = new RNGCryptoServiceProvider();
+        private static Random _random_gen = new Random();
+        private static int _min_iteration_count = 4000;
+        private static int _max_iteration_count = 5000;
+        private const int _sha_output_length = 20;
+
+        private static byte[] ComputeHMACHash(byte[] data, string secret)
+        {
+            using (var _hmac_sha_1 = new HMACSHA1(data, true))
+            {
+                byte[] _hash_bytes = _hmac_sha_1.ComputeHash(Encoding.UTF8.GetBytes(secret));
+                return _hash_bytes;
+            }
+        }
+
+        public static string AnswerChallenge(string challenge, string secret)
+        {
+            var components = new Dictionary<string, string>();
+            var parts = challenge.Split(',');
+            foreach(var part in parts){
+                var subParts = part.Split(new char[] { '=' }, 2);
+                components.Add(subParts[0], subParts[1]);
+            }
+
+            var iterations = int.Parse(components["i"]);
+            var salt = components["s"];
+            var salted = Hi(secret, Convert.FromBase64String(salt), iterations);
+
+            return Convert.ToBase64String(ComputeHMACHash(salted, secret));
+        }
+
+        public static string GetChallenge()
+        {
+            var numIterations = GetRandomInteger();
+            return "i=" + numIterations + ",s=" + Convert.ToBase64String(GetRandomByteArray(_nonce_byte_length));
+        }
+
+        private static byte[] Hi(string password, byte[] salt, int iteration_count)
+        {
+            Rfc2898DeriveBytes _pdb = new Rfc2898DeriveBytes(password, salt, iteration_count);
+            return _pdb.GetBytes(_sha_output_length);
+        }
+
+        private static int GetRandomInteger()
+        {
+            if (_random_gen == null)
+                _random_gen = new Random();
+
+            int _random_int = _random_gen.Next(_min_iteration_count, _max_iteration_count);
+
+            if (_random_int < 0)
+                _random_int *= -1;
+
+            return _random_int;
+        }
+
+        private static byte[] GetRandomByteArray(int byte_array_length)
+        {
+            byte[] _random_byte_array = new byte[byte_array_length];
+
+            _random_crypt_prov.GetBytes(_random_byte_array);
+
+            return _random_byte_array;
+        }
+    }
+}