Added registration.

Currently doesn't return any valid result, hence host believes device
failed to register, however, insecure storage of keys does occur.

Readme.AttestationCertificateGeneration.txt

@@ -0,0 +1,45 @@
+From https://github.com/pratikd650/Teensy_U2F/blob/master/Teensy_U2F.cpp line 292
+
+Instructions to generate attestation certificate using open ssl
+https://wiki.openssl.org/index.php/Command_Line_Elliptic_Curve_Operations
+https://www.guyrutenberg.com/2013/12/28/creating-self-signed-ecdsa-ssl-certificate-using-openssl/
+ P-256 (also secp256r1)  EC key pair is    W = dG   (Note secp256k1 is Koblitz curve - not P256)
+ d = private key is it 256 bits (32 bytes)
+ G = generator point - it is part of the curve definition
+ W = public key point - it is a (256, 256) bits  - 64 bytes
+1) generate a key pair - the private key will be saved in PKCS8 format in ecprivkey.pem
+openssl ecparam -name prime256v1 -genkey -noout -out ecprivkey.pem
+2) dump out the private key in hex format - it will be a 32 byte key
+ openssl asn1parse  -in ecprivkey.pem
+3) compute the public key from the private key and the curve
+openssl ec -in ecprivkey.pem -pubout -out ecpubkey.pem
+4) dump out the public key in hex format - it will be 66 byte - the first two bytes are 00 04,
+  openssl ec -in ecprivkey.pem -pubout -text
+  after that is the point W - 32 byte + 32 byte
+5) generate a self signed certificate
+  openssl req -new -x509 -key ecprivkey.pem -out server.pem -days 3650
+For the Certificate name give a unique certificate name. There is a 128 bit unique identification number burned into every
+Teensy chip  - see http://cache.freescale.com/files/32bit/doc/data_sheet/K20P64M72SF1.pdf
+You can print out the number from your Teensy using this simple program given below
+6) Display the certificate
+  openssl x509 -in server.pem -text -noout
+
+7) Convert PEM certificate to DER
+openssl x509 -outform der -in server.pem -out certificate.der
+
+8) Generate a usable c-array for source code
+xxd --include certificate.pem
+
+Copy output into appropriate array in 'Certificates.cpp', overwriting existing values
+
+9) Repeat steps 7 & 8 for public key and private key
+
+So:
+`
+openssl asn1parse -in ecprivkey.pem 2>/dev/null | grep 'HEX DUMP' | perl -pe 's/^.*\[HEX DUMP\]:(.+)$/$1/' 2>/dev/null | xxd -r -p > privkey.der && xxd --include privkey.der
+
+openssl ec -in ecprivkey.pem -pubout -text 2>/dev/null | perl -0777 -ne 'print /pub:.+ASN1/sg' 2>/dev/null | sed -e '/pub:/d;/ASN1/d' | perl -pe 's/^\s+(.+):?$/$1/gm' 2>/dev/null | perl -pe 's/\n//' 2>/dev/null | perl -pe 's/(.{2}):?/$1/g' 2>/dev/null | xxd -r -p > pubkey.der && xxd --include pubkey.der
+`
+and copy the arrays into the correct arrays in Certificates.cpp
+
+If any arrays have different lengths than shown in Certificates.hpp, update these too.