Add the SM4 block cipher, also a no-padding option for block ciphers.

This adds an implementation of the SM4 block cipher, and operations
to encrypt and decrypt using it with CBC,ECB,CFB,OFB,CTR modes.

Also, a "no padding" option is added for AES,DES,3DES and SM4
decryption in ECB/CBC modes. This variant does not attempt to
validate the last block as being PKCS#7 padded.

This is useful, both since other padding schemes exist, and also
for decrypting data where the final block is missing.

src/core/config/Categories.json

@@ -83,6 +83,8 @@
             "ROT47",
             "XOR",
             "XOR Brute Force",
+            "SM4 Encrypt",
+            "SM4 Decrypt",
             "Vigenère Encode",
             "Vigenère Decode",
             "To Morse Code",