Java 8/Junit 5 Migration

[gribnut]

Was having a fair number of warnings/issues compiling for Java 8/11 so thought I'd update some of the code for use with current supported JVMs. Mainly updates to migrate toward Java 8/11 code style.

• Set type and checks for raw maps, lists, sets, classes, etc.
• Migrate to Junit 5
• Some additional unit tests for RadiusAttribute subclasses (additional unit tests still needed)
• Minor code changes/cleanup for Java 8+

I only use library with RADIUS client so server code not tested. Feel free to merge changes or toss as see fit. Happy to make additional changes if needed.

[ctran]

Appreciate the effort. I'll need some time to review all the changes.

[gribnut]

Merged recent CI changes and fixed sonatype lift warnings (the ones marked new anyway).