Crc16 and DlmsReader ported from C# project. Working condition

Code/ESPDebugger/Crc16.cpp

@@ -0,0 +1,37 @@
+#include "Crc16.h"
+
+Crc16Class::Crc16Class()
+{
+    unsigned short value;
+    unsigned short temp;
+    for (unsigned short i = 0; i < 256; ++i)
+    {
+        value = 0;
+        temp = i;
+        for (byte j = 0; j < 8; ++j)
+        {
+            if (((value ^ temp) & 0x0001) != 0)
+            {
+                value = (ushort)((value >> 1) ^ polynomial);
+            }
+            else
+            {
+                value >>= 1;
+            }
+            temp >>= 1;
+        }
+        table[i] = value;
+    }
+}
+
+unsigned short Crc16Class::ComputeChecksum(byte *data, int start, int length)
+{
+    ushort fcs = 0xffff;
+    for (int i = start; i < (start + length); i++)
+    {
+        byte index = (fcs ^ data[i]) & 0xff;
+        fcs = (ushort)((fcs >> 8) ^ table[index]);
+    }
+    fcs ^= 0xffff;
+    return fcs;
+}