GUACAMOLE-839: Use BouncyCastle for retrieval of certificate details.

Java's build-in support for reading X.509 certificates does not deal
well with PIV certificates containing the username as a "serialNumber"
attribute. Rather than exposing the string value of that attribute, the
Java implementation exposes a byte array that does not fully match the
string value shown by a tool like OpenSSL.

BouncyCastle, on the other hand, _does_ match the output of OpenSSL, and
provides a predictable means of decoding the certificate.

doc/licenses/bouncycastle-pkix-fips-1.0.7/README

@@ -0,0 +1,8 @@
+BouncyCastle PKIX APIs, FIPS Distribution (https://www.bouncycastle.org/fips-java)
+-----------------------------------------------------------------------
+
+    Version: 1.0.7
+    From: 'The Legion of Bouncy Castle' (https://www.bouncycastle.org)
+    License(s):
+        MIT (bundled/bouncycastle-pkix-fips-1.0.7/LICENSE)
+