Upgrade to correct version of BouncyCastle

The existing Maven dependencies are for org.bouncycastle:bcprov-jdk16:1.46 and org.bouncycastle:bcpg-jdk16:1.46. While jdk16 looks "newer" than jdk15on, this was actually a legacy mistake on the part of BouncyCastle versioning. The correct and current version of BouncyCastle is jdk15on, as evidenced by the age of the releases:

• jdk15on: 03/2012 - 10/2015 "The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.8." (http://mvnrepository.com/artifact/org.bouncycastle/bcprov-jdk15on)
• jdk16: 11/2007 - 02/2011 "The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.6." (http://mvnrepository.com/artifact/org.bouncycastle/bcprov-jdk16)