Migrate code base from Java 8 to Java 11

[knjensen]

Change the Maven pom code level from 8 to 11, and correct findings. Known issues:

• Reflection; Changes between 8 & 11 must be addressed
• JavaDoc; As of Java 9, there's problems - should be fixed in later Java versions, left for now
• Support for newer Crypto features, eg. Elliptic Curve should also be added.
• Consider dropping support for SOAP, due to changes with Java 9+ & XML libraries

Also, ensure that there is a 1.x branch made, which will exists until the official Java 8 support ends. Git Master should be 2.x

[knjensen]

With the previous commit, the migration should be complete. The SOAP will be dropped as part of #70.