ldaptive v2 patch

Hello devs, I created a branch that contains the code changes needed to migrate ldaptive from v1 to v2. I'm not sure what your plans are in terms of Java 8/11 and Grouper 2.5/2.6, but I thought it would be useful for someone to review those changes. If nothing else it should help from a planning perspective.

https://github.com/dfish3r/grouper/tree/ldaptive-v2

These changes do build successfully but I wasn't able to run the docker based tests on my system. I'd be happy to work through errors if someone is willing to post the output.