Replacing TreeSet with AVLTreeSet

[David McManamon <dm...@gmail.com>]

There were interesting papers regarding balanced binary trees in 2015 & 2016

http://sidsen.azurewebsites.net//

And after reading about "Rank-balanced Trees"  I started comparing AVL &
Red-black tree performance and was surprised to see that red-black trees
are the default in Java given the performance differences noted in Ben
Pfaff's 2004 work.
So I wrote several new TreeMap implementations and put them on GitHub with
two short blog posts-

https://refactoringlightly.wordpress.com/

Seems that TreeSet is used a lot in Lucene and if the input has sequences
then the constants in the Olog(n) operations make those places a very
strong candidate to switch to an AVLTreeSet.

So many uses of TreeSet I wasn't sure where/how to start benchmarking?

--David